Tomic was born in Stuttgart, Germany, on 21 October 1992. Tomic’s parents, Croatian father, John (Ivica) and Bosnian mother, Ady (Adisa), left Socialist Yugoslavia several years before his birth. In an interview, Tomic stated that his parents “have a Croatian background”. They were both working in Germany when Tomic was born. The family migrated to Gold Coast, Queensland, Australia in 1996 when Tomic was three years old. His younger sister Sara is also a professional tennis player. Tomic was educated at Southport State School during his primary school years before taking up a sports scholarship at The Southport School for high school.

Before Tomic began competing on the ITF junior tour he stated that he would become the number 1 tennis player in the world, win all the Grand Slams and become Australia’s youngest Davis Cup player. He also claimed he would achieve these goals by attaining the serve of Goran Ivanišević, the mind of Pete Sampras, the groundstrokes of Roger Federer and the heart of Lleyton Hewitt. In 2004, 2006 and 2007 respectively, Tomic won the 12s, 14s and 16s Orange Bowl titles – one of the most prestigious events on the junior tour.

Playing his first singles event on the ITF junior tour in 2006, he qualified for the Sunsmart 18 and Under Canterbury Championships in New Zealand and went on to win the title at 13 years of age, defeating Dae-Soung Oh of Korea in the final. His success continued in the following weeks, winning the next three tournaments he played in, giving him a 25 match winning streak. He was able to extend this streak to 26 at the Riad 21 junior tournament in Morocco before falling in the round of 16 to future junior world number 1 and ATP top 50 player Ričardas Berankis.

In March 2006, a 13-year-old Tomic signed a six-figure deal with sports marketing and management giant IMG. Prior to joining the ITF juniors tour in 2007, Tomic played with Wilson racquets but switched to Head when he debuted on the junior tour. At the beginning of the 2012 ATP season Tomic signed a deal to use Yonex racquets. Bernard again switched to Head racquets, but was later dropped by the racquet manufacturer following a post match press conference at the 2017 Wimbledon.

Tomic did not play in another tournament until August 2007, where he won the Oceania Closed Junior Championships without dropping a set. He was unable to continue his dominance at the Junior US Open, falling in the Round of 16 to future top 15 ATP player Jerzy Janowicz. Following the US Open, Tomic picked up a second title in 2007 by winning the G1 in Kentucky. He would then travel to Italy where he compiled an undefeated record in the Junior Davis Cup and lead Australia to victory in the final against Argentina with teammates Mark Verryth and Alex Sanders. Tomic finished 2007 with a junior world ranking of 23.

Tomic began 2008 by winning Nottinghill, an Australian ITF Junior event in Melbourne without dropping a set. Two days later he started his campaign for the Australian Open Juniors title as the 5th seed. He went on to win the event, defeating the 25th, 11th, 8th and 1st seed before beating 10th seed Tsung-Hua Yang of Taiwan in the final. His win at the age of 15 made him the youngest winner of the Australian Open Junior Boys’ Championships in the Open Era.

In August, Tomic reached the first professional final of his career at an F2 tournament in Indonesia. He defeated Kittipong Wachiramanowong, Hsien-Yin Peng, Peerakiat Siriluethaiwattana and Kento Takeuchi en route to the final without dropping a set before losing to Yūichi Sugita in three sets. In December, Tomic competed at a F12 tournament in Australia where he defeated fellow Australian James O’Brien in the first round before controversially walking off court whilst down a set and 3–1 against Marinko Matosevic in his next match. Towards the end of 2008, Tomic stated that he would no longer compete in junior tournaments and instead focus solely on senior tournaments. In March 2009, the ITF suspended Tomic from playing ITF professional tournaments for a month.

In January 2009, Tomic was granted a wildcard into his first ATP event, the Brisbane International, where he lost to Fernando Verdasco in the first round. He was also granted a wildcard into the 2009 Australian Open, drawing Potito Starace in the first round. He won the match after saving two set points in the fourth set tiebreak and thus became the youngest ever male tennis player to win a senior Australian Open Grand Slam tournament match. In the second round he lost to Gilles Müller in four sets. Tomic also contested the mixed doubles event with fellow 16-year-old Australian Monika Wejnert but the pair lost to the Canadian pairing of Aleksandra Wozniak and Daniel Nestor in the first round.

Following the defeat, Tomic decided to return to the junior tour to contest the Grand Slam tournaments and reached the quarterfinals of the French Open Junior tournament. At Wimbledon, Tomic lost in the final round of qualifying to Édouard Roger-Vasselin. He contested the junior tournament and reached the semi-finals before being losing to the eventual champion, Andrey Kuznetsov. In September, Tomic won the 2009 US Open Junior singles title by defeating Chase Buchanan in the final. In December 2009, Tomic lost in the final of the Australian open wildcard playoff to Nick Lindahl. He finished the year as the World No. 286.

At 2009 Wimbledon, at which Tomic was contesting the junior event, Lleyton Hewitt contacted the Tomic camp inviting Bernard to practice. Hewitt’s physiotherapist Iván Gutiérrez was told by Tomic’s agent: “No, he’s not hitting with Lleyton, Lleyton’s not good enough.”

Tomic began the 2010 season by competing in the 2010 Brisbane International where he lost in the first round to qualifier Alexandr Dolgopolov. He won the World Tennis Challenge for the Australasia team, defeating Gilles Simon of team Europe, Radek Štěpánek of the Internationals team and Robby Ginepri of the Americas team. At 2010 Kooyong Classic Tomic defeated World No. 3 Novak Djokovic in three sets (6–4, 3–6, 7–5). Despite losing in the wildcard playoff, Tomic was granted a main draw wildcard for the 2010 Australian Open. At the Australian Open, Tomic defeated Guillaume Rufin in the first round in straight sets before losing to fourteenth seed Marin Čilić in the second round in five sets.

In February, Tomic qualified for the Burnie Challenger tournament in Tasmania and went on to win the event by defeating Greg Jones in the final. In March, Tomic was selected to play singles for the Australian Davis Cup Team. He won both of his matches in the tie against Chinese Taipei, defeating Yang Tsung-hua and Lee Hsin-han. He then competed at the 2010 Tennis Napoli Cup as a wildcard but lost to Paolo Lorenzi in the first round in straight sets. Tomic’s next tournament was the 2010 Monte-Carlo Rolex Masters where he lost in the first round to the unseeded German Benjamin Becker. He then received a wildcard to compete in the 2010 Zagreb Open but lost to Michael Yani in the first round.

Tomic was awarded a wildcard for the 2010 Aegon Championships where he upset fifteenth seed Andreas Seppi in the first round before losing to Belgian Xavier Malisse in the second round. At the 2010 Wimbledon Championships, Tomic qualified for the main draw but lost in the first round to Mardy Fish. He then entered the qualifying draw of the 2010 US Open but lost in the second round to Noam Okun. His final ATP event of the year was the 2010 Proton Malaysian Open where he competed as a wildcard. He lost to David Ferrer in the first round. In December 2010, Tomic withdrew from the Australian Open Wild Card Play Offs. He finished the year at a career high singles ranking of world No. 208.

Tomic made his Davis Cup debut for Australia in Melbourne against Chinese Taipei in 2010 at the age of 17 years and 135 days, the youngest ever player for Australia. In the first rubber of the tie Tomic defeated Yang Tsung-hua. In the fifth rubber he picked up another victory over Lee Hsin-han.

In 2010, Tomic won the World Tennis Challenge for the Australasia team. Tomic won all three singles matches, defeating Gilles Simon, Radek Štěpánek and Robby Ginepri.

In February, Tomic competed in the 2011 BNP Paribas Open, where he was given a main draw wild card. In the first round, Tomic defeated Indian qualifier Rohan Bopanna in three sets to reach the second round of an ATP Masters 1000 tournament for the first time. He faced sixteenth seeded Serbian, Viktor Troicki in the second round where he lost in straight sets. Tomic was granted a main draw wild card for the Sony Ericsson Open in Miami but lost in the first round to Pablo Andújar. At the French Open he lost in the first round to Carlos Berlocq, in straight sets.

At the 2011 Wimbledon Championships, Tomic defeated twenty-eighth seed Nikolay Davydenko, Igor Andreev, fifth seed Robin Söderling and Xavier Malisse to reach his first grand slam singles quarterfinal, thus becoming the youngest player since Boris Becker in 1986 to reach the quarterfinals at Wimbledon. There, he lost to the eventual champion Novak Djokovic in four sets. With this showing, Tomic moved 87 places up in the ATP rankings, to number 71 in the world.

Tomic then returned home to Australia to compete in the 2011 Davis Cup World Group Play-offs against Switzerland. He defeated Stanislas Wawrinka in the opening match but lost his second match to world No. 3 Roger Federer. Tomic then competed at the 2011 Proton Malaysian Open but lost in the first round to Flavio Cipolla. Tomic’s next event was the 2011 Rakuten Japan Open Tennis Championships. He upset the fifth seed, Victor Troicki in straight sets in the first round and defeated Japanese wildcard Tatsuma Ito in the second round before losing to fourth seed Mardy Fish in the quarterfinals. Tomic achieved a new career high singles ranking of world No. 49 following the event. Tomic then entered the Shanghai Masters where despite being unseeded, he reached the third round. Tomic defeated Kevin Anderson and 5th seed Mardy Fish before losing to Alexandr Dolgopolov. He then competed at the 2011 If Stockholm Open. He defeated qualifier, Jürgen Zopp in the first round but lost to Gaël Monfils in the second round. Tomic finished the year ranked world No. 42.

Tomic was called back into the team in July 2011 for the tie against China. Following a shock loss in the first match, Tomic drew Australia level in the second rubber of the tie against Zhang Ze. Tomic’s reverse singles match was cancelled due to Australia winning the tie 3–1. In September 2011 at the Davis Cup World Group Playoffs Tomic pulled off the biggest scalp of his Davis Cup career by defeating world number 19 Stanislas Wawrinka in four sets. In the reverse rubber, Tomic faced his childhood hero Roger Federer, losing in four sets.

Prior to the commencement of the 2012 ATP season, Tomic and Lleyton Hewitt both committed to the Davis Cup team for all ties in a bid to re-enter the world group. In the second rubber of the first zonal tie against China, Tomic was victorious against Wu Di. In the second zonal tie of 2012, he recorded two straight sets victories in a 5–0 rout of South Korea. In the 2012 Davis Cup World Group Playoffs, Tomic was victorious in his first rubber against Cedrik-Marcel Stebe in four sets but fell to Florian Mayer in straight sets which would see Australia lose to Germany 3–2 overall.

Following poor off court behaviour in late 2012, Tomic was suspended from playing for Australia in the first round of the 2013 Davis Cup competition. After serving a one tie ban, Tomic returned to the Australian Davis Cup team in their 2013 zonal semifinal against Uzbekistan and later that year was instrumental in Australia’s return to the World Group after an away playoff victory over Poland. Injuries prevented Tomic from competing in the Davis Cup competition in 2014 but he returned for Australia’s first round of the 2015 Davis Cup against the Czech Republic. Despite facing the two-time defending champions away, Tomic secured two crucial singles victories and led Australia to a 3–2 victory over the Czech Republic. It was the first time Australia had reached the second round of the Davis Cup world group since 2006. Tomic was then once again suspended from the Australian Davis Cup team for an outburst during a Wimbledon press conference. Tomic returned to the team once again in the 2015 semifinal against Great Britain and scored a crucial four set victory over Dan Evans in the second rubber. Tomic played for Australia at the 2016 Davis Cup where they faced the United States. He won his first match against Jack Sock in four sets. However, he lost the reverse singles to John Isner which meant Australia lost in the first round.

Tomic was first coached by Gold Coast tennis instructor Neil Guiney at age 7. As a child Tomic was officially coached by his father, John, at Queens Park Tennis Centre on the Gold Coast. Despite his father never having played tennis, he continues to coach Tomic. In November 2012 it was revealed that Tomic had approached Australian tennis legend Pat Cash to coach him on a full-time basis. Cash declined the offer. As of 2016, Tomic was training out of Koza World of sports tennis academy with Australian coach Gavin Hopper.

In January 2012, he was fined by the police on the Gold Coast three times in one day. Later that day he also ran from the police and locked himself in his house. In November 2012, Tomic pleaded guilty in court to failing to stop for police in his orange BMW M3 and was fined $750, as well as being put on a 12-month good-behaviour bond. Tomic accused a police officer of trying to hit him. He was also found guilty of three other traffic offences committed in January and was fined a further $1000.

At the 2013 Hopman Cup Tomic defeated Tommy Haas, World No. 1 Novak Djokovic and Andreas Seppi. Tomic’s first official tournament for the year was the Apia International in Sydney. He defeated compatriot Marinko Matosevic, fifth seed Florian Mayer, defending champion Jarkko Nieminen and Andreas Seppi in the semifinals to reach his first career singles final where he defeated Kevin Anderson in three sets to win his maiden ATP title. At the 2013 Australian Open, Tomic defeated Leonardo Mayer and Daniel Brands to reach the third round where he lost to world No. 2 Roger Federer in straight sets.

Tomic’s first tournament following the US open was in Bangkok where he defeated Ivo Karlović to reached the second round before losing to Gilles Simon. Then Tomic took part in the 2013 China Open – Men’s Singles, in the first round, he defeated Zhang Ze before losing to fifth seed Richard Gasquet in the second round. This was the first of five consecutive main draw losses, which included losing to Jérémy Chardy in Shanghai, Jack Sock in Stockholm, Mikhail Youzhny in Valencia and Feliciano López in Paris to close out his 2013 season. He finished the year ranked world No. 51.

At the 2013 Hopman Cup Tomic defeated Tommy Haas (7–6, 3–6, 7–5), World No. 1 Novak Djokovic (6–4, 6–4) and Andreas Seppi (6–3, 7–5). Australia finished in 2nd place in the group.

In 2013, John Tomic was sentenced to eight months in prison and banned from the ATP World Tour for 12 months for headbutting and breaking the nose of Bernard’s hitting partner, Thomas Drouet. However, Tomic Sr. did not face a jail term.

At the 2014 Hopman Cup Tomic lost to Milos Raonic but then he defeated Andreas Seppi and Grzegorz Panfil. Tomic started off his 2014 season attempting to defend his Sydney International crown. In the first round, he crushed eighth seed Marcel Granollers, dropping just three games. He then defeated to Blaž Kavčič in the three sets to reach the quarterfinals where he had a straight sets win over Alexandr Dolgopolov. In the semifinals he faced Sergiy Stakhovsky, coming from a set down to advance to the final. In the final, he was defeated easily by world No. 6 Juan Martín del Potro. His next tournament was the 2014 Australian Open, where he retired in the first round against Rafael Nadal with a groin injury.

At the 2014 Stockholm Open, Tomic defeated Patrik Rosenholm, Kevin Anderson and Fernando Verdasco into the semi-final, he lost to Grigor Dimitrov.

At the 2014 Hopman Cup Tomic lost to Milos Raonic (6–7, 1–6) but then he defeated Andreas Seppi (4–6, 6–3, 6–2) and Grzegorz Panfil (6–1, 6–4). Australia team finished in last place in the group.

Tomic then competed for Australia at the Davis Cup Semifinals and defeated Daniel Evans which saw him crack the top 20 in the rankings for the first time. Following his win he lost in straight sets to world number 3 Andy Murray. His next tournament was the Japan Open where he retired whilst down a set against Steve Johnson. Tomic then entered the Shanghai Masters where despite being unseeded, he reached the quarterfinals. Tomic defeated Fernando Verdasco, 7th seed David Ferrer and Richard Gasquet before losing to world number one Novak Djokovic 7–6, 6–1. This was the most games any player had won against Djokovic in 8 matches. The tournament scored Tomic his 3rd top 10 win in 2015 (over David Ferrer) and was also his 2nd Masters quarterfinal of his career. As a result of his performance, he propelled to world number 18 for the first time. Tomic next played at the 2015 Stockholm Open as the 4th seed where he lost to Marcos Baghdatis in the second round after a first round bye. His final tournament of the year was the Paris Masters where he defeated Fabio Fognini before losing to eventual semi finalist Stan Wawrinka in the second round. He finished the year ranked world No. 18.

In July 2015 Tomic was arrested in Miami and charged with resisting arrest and trespassing. In October, all charges were dropped against Tomic.

Following his ranking slide, Tomic entered the qualifying tournament at the Australian Open as the 29th seed. He advanced to the final round before losing to unheralded Italian Lorenzo Sonego. This marked the first time since 2008 that Tomic had failed to appear in the main draw of the Australian Open. Following his loss in qualifying, Tomic entered reality television show I’m a Celebrity…Get Me Out of Here. Tomic quit the competition after three days, proclaiming a desire to return to tennis as the primary reason. After this, Tomic was awarded a wildcard into the 2018 Istanbul Open where he served for the match against 6th seed Viktor Troicki in the first round, however, he went on to lose the match. Tomic’s hiatus coupled with poor results blew his ranking out to 243 in the world, his worst ranking since 2010. Tomic then entered a challenger tournament in France where he scored three consecutive wins for the first time since Cincinnati in 2016. He made the final but was defeated by compatriot and top seed John Millman. The result improved his ranking to 191. Tomic then qualified for the French Open and was expected to face compatriot Nick Kyrgios in a hotly anticipated first round match-up. Kyrgios however withdrew before the tournament from an elbow injury, leaving Tomic to face lucky loser Marco Trungelliti. Tomic went on to lose the match in four sets.

In the 2016 US Open, during his first round loss to Damir Džumhur, he verbally abused a spectator after apparently being taunted.

On 9 January 2017, Bernard Tomic defeated Dominic Thiem 3–4 4–2 4–3 3–4 5–3 to win the event. Before this match, Nick Kyrgios defeated Rafael Nadal 4–3, 2–4, 4–3 4–3. With Australia leading 2–0, the doubles were not played.

Tomic then attempted to qualify for the Stockholm Open, but was forced to retire from injury in the first-round of qualifying against Oscar Otte. Tomic played no further tournaments in 2018 and finished the year ranked world No. 83.

He previously held a long-standing sponsorship deal with Nike, before switching to Lacoste in 2018. Tomic wore Lotto clothing during the 2018 French Open qualifying, but was wearing Lacoste by the main draw. Tomic wore Mizuno clothing for the first time at the start of the 2019 season.