Marcus Earl Stroman was born in Medford, New York, on May 1, 1991. He attended Patchogue-Medford High School in Medford, and was drafted in the 18th round of the 2009 MLB draft (532nd overall) by the Washington Nationals. He opted not sign, and instead entered Duke University, where he played college baseball for the Duke Blue Devils baseball team.

In 1997, a six-year-old Stroman made an appearance on the Nickelodeon game show Figure It Out.

At Duke, Stroman compiled a career record of 15–13 in 48 appearances, and set the Duke record for career strikeouts (290 over 222 innings pitched). He was also a position player for Duke, making 97 appearances, mostly at second base and shortstop. In 2010 and 2011, he played collegiate summer baseball for the Orleans Firebirds of the Cape Cod Baseball League, and was named a league all-star in 2010.

Billed by analysts as the most major league ready player available in the 2012 MLB draft, Stroman was drafted by the Jays 22nd overall, and became the first Duke player ever selected in the first round. After starting his professional career with the Low-A Vancouver Canadians, the Blue Jays promoted Stroman to the Double-A New Hampshire Fisher Cats on August 1, 2012. Stroman was suspended for 50 games on August 28, 2012, for testing positive for methylhexanamine, a banned stimulant.

Having completed his suspension, Stroman started and pitched five scoreless innings to get the win in the May 19, 2013 game for the Fisher Cats. On July 2, 2013, Stroman struck out 13 batters over 6⁄3 innings in a 3–1 loss to the New Britain Rock Cats. He was ranked as the number 3 prospect in the Blue Jays organization on July 26, 2013, when the revised Top 100 Prospects list was released.

Stroman was called up to the Blue Jays on May 3, 2014, after Brandon Morrow was transferred to the 60-day disabled list. At the time of his call-up, he was considered the organization’s number two prospect. He earned his first MLB victory on May 6, pitching 1⁄3 innings in relief of Drew Hutchison. Stroman was optioned back to Triple-A Buffalo on May 18, and was recalled on May 30 to make his first Major League start the following day. He pitched six innings and surrendered only one earned run on five hits, striking out six and issuing no walks to earn the win over the Kansas City Royals. On August 9, Stroman pitched nine innings for the first time in his career, but came away with a no-decision as the Blue Jays defeated the Detroit Tigers 3–2 in extra innings. He would earn his first complete game and shutout on September 8, needing only 93 pitches to beat the Chicago Cubs, 8–0. Stroman yielded only three hits and at one point had retired 19 consecutive batters.

On October 6, 2014, Stroman announced through his Twitter account that he would change his uniform number from 54 to 6 in honor of his grandmother. During 2015 spring training, Stroman suffered a torn anterior cruciate ligament in his left knee. He underwent a successful surgery, performed by Dr. James Andrews, to repair his ACL. Stroman was placed on the 60-day disabled list on April 5. While rehabbing the injury, Stroman returned to Duke University to finish his degree, majoring in Sociology with a minor in Markets and Management Studies.

On January 9, 2015, Stroman completed the legal process for trademarking “Height Doesn’t Measure Heart” and “HDMH”. Since mid-2015, he has produced caps with New Era that feature his trademarks. He has also partnered with Nike, Jordan Brand, BioSteel, and Rogers to create apparel featuring the HDMH logo. Stroman stated in December 2016 that he measured exactly 5′ 7.25″ for a physical examination for Nike.

On May 15, 2016, Stroman graduated from Duke University with a bachelor’s degree in sociology.

On March 23, 2016, Stroman was named the Opening Day starter for the Blue Jays. He pitched into the ninth inning, holding the Tampa Bay Rays to three runs on six hits, while striking out 5 in a 5–3 win. Stroman established a new career-high in strikeouts, with 9, in a 5–1 win over the Rays on May 1. He also set a Blue Jays franchise-record for strikeouts on a pitcher’s birthday, surpassing David Price, Marc Rzepczynski, and Roy Halladay, who each had 8 strikeouts in starts on their birthdays. Stroman improved on his single-game strikeout record on August 1, when he struck out 13 Houston Astros batters in a no-decision. He finished the 2016 regular season with a 9–10 record, 4.37 ERA, and 166 strikeouts over a career-high 204 innings pitched. He had the highest ground ball percentage among major league pitchers (60.1%), and the lowest fly ball percentage (20.4%).

In December 2016, Stroman announced that he would play for Team USA at the 2017 World Baseball Classic. He made three starts for the team, and posted a 2.35 ERA in 15⁄3 total innings. In the final game, Stroman held Team Puerto Rico scoreless and without a hit through six innings, leading Team USA to an 8–0 victory and their first WBC championship. Following the game, Stroman was named the tournament’s most valuable player (MVP). He was also named to the All-World Baseball Classic team.

On February 14, 2017, it was announced that Stroman had won his arbitration case and would receive a $3.4 million salary for the 2017 season. In a 6–5 win over the St. Louis Cardinals on April 25, Stroman recorded the first hit of his career. His double to left field was the first ever pinch hit by a Blue Jays pitcher, and also the first extra-base pinch hit by an American League pitcher since Gary Peters in 1971. Stroman hit an opposite field home run off Julio Teherán in the Blue Jays 9–0 win over the Atlanta Braves on May 18, 2017. In doing so, Stroman became just the second Blue Jays pitcher to hit a home run, joining Mark Hendrickson, who did so on June 21, 2003. Stroman’s home run followed Luke Maile’s solo shot, making the batterymates the first to hit back-to-back home runs since 1970. He also became the first pitcher listed 5′ 8″ or shorter to hit a home run in the majors since Tom Phoebus of the Baltimore Orioles did so in 1968. On July 3, Stroman left a game against the New York Yankees after five innings when a blister developed on his right middle finger, though the injury did not cause him to miss a start. Stroman was hit on the right elbow by a line drive in Toronto’s 7–2 win over the Baltimore Orioles on September 2, and was forced to leave the game, though he was once again able to make his next start.

Stroman finished the 2017 season with 13 wins, 164 strikeouts, and a 3.09 ERA in 201 innings. By passing the 200-inning mark, he became the seventh Blue Jays pitcher in the prior 20 years to have consecutive 200-inning seasons. He again had the highest ground ball percentage among major league pitchers (62.1%), and the lowest fly ball percentage (19.7%). He gave up the longest home run of all major league pitchers in 2017, at 496 feet.

On February 15, 2018, Stroman announced through his Twitter account that he had lost his arbitration case and would make $6.5 million for the season instead of his requested salary of $6.9 million. Stroman struggled to start the 2018 season, going 0–5 with a 7.71 ERA before being placed on the 10-day disabled list due to right shoulder fatigue on May 11. On June 13, he made his High-A debut with the Dunedin Blue Jays and pitched 4⁄3 innings in a rehab start, surrendering two runs on one hit while walking four and striking out three. Stroman returned to Toronto’s rotation on June 23, pitching five shutout innings against the Los Angeles Angels. Later in the season, Stroman was forced to leave starts on August 7 and 17 against the Boston Red Sox and New York Yankees, respectively due to blisters in his pitching hand. He would return again on September 3 to start against the Tampa Bay Rays, however, blisters again forced him out of the game. Stroman would not return again in 2018 after this start, ending his 2018 season with a 4–9 record and a 5.54 ERA in 19 starts.

On March 13, 2019, Stroman was announced as the Opening Day starter by Blue Jays manager Charlie Montoyo. On June 30, Stroman was named to the 2019 MLB All-Star Game, his first all-star nomination of his career.

On July 28, 2019, the Toronto Blue Jays traded Stroman (along with cash considerations) to the New York Mets for pitching prospects Anthony Kay and Simeon Woods Richardson.. In 11 starts with the Mets in 2019, Stroman was 4–2 with a 3.77 ERA and 60 strikeouts. He finished 10–13 with a 3.22 ERA overall between the Blue Jays & Mets.

On November 15, 2019, Stroman announced via Twitter he was switching to number 0 for the 2020 season and also changed his Twitter handle to @STR0. Earlier in the offseason, he stated he wanted to give up No. 7 in honor of Jose Reyes. That offseason, he also hired Nikki Huffman as his personal trainer, away from the Toronto Blue Jays where she served as head trainer. He first met her in 2015 at Duke University where she helped him recover from a torn ACL ahead of schedule.. Stroman missed the beginning of the 2020 season with a torn left calf muscle. On August 10, 2020, before his return, he announced he would opt out of the season.

After the 2020 season, the Mets extended a qualifying offer to Stroman worth $18.9 million for the 2021 season. Stroman accepted the qualifying offer on November 11.