Darvish attracted national attention when he pitched a no-hitter against Kumamoto Technical High School in the first round of the 76th National High School Baseball Invitational Tournament as a senior on 26 March 2004. The team lost in the quarter-finals despite stellar outings by Darvish and sidearmer Kenji Makabe (currently with Honda Motor Company’s industrial league team). He pitched 12 games and put up a 7–3 record with 87 strikeouts in 92 innings pitched and a 1.47 ERA in his four national tournament appearances, and posted a 1.10 ERA for his high school career, striking out 375 in 332⅓ innings (67 appearances).

Darvish was considered one of the best high school pitchers in the 2004 NPB amateur draft along with Yokohama Senior High School right-hander Hideaki Wakui (later picked by the Seibu Lions) and Akita Municipal Akita Commercial High School right-hander Tsuyoshi Sato (Hiroshima Toyo Carp). While the Fighters, Carp, Chunichi Dragons, Fukuoka Daiei Hawks and Orix BlueWave all considered selecting Darvish with their first-round pick in the final months, the Fighters were one of the few teams that chose not to forgo the first round in exchange for signing a college or industrial league player prior to the draft. This enabled them to land Darvish with their first-round pick in 17 November draft, signing him to a base salary of 15 million yen, a signing bonus of 100 million yen and additional performance-based incentives (the equivalent of what a first-round college or industrial league player would normally receive) on 17 December.

Darvish received further publicity when he was caught smoking in a pachinko parlor on an off-day during his first Spring training in 2005, despite not being old enough to legally smoke nor to gamble at the time. The incident prompted his high school to suspend him, and the Fighters to place him under probation for an indefinite period and order him to participate in community service.

Darvish had a breakout year in 2006, compiling a 12–5 record with 115 strikeouts and a 2.89 ERA. In particular, he went 10–0 after 30 May, playing a leading role in the Fighters’ first Pacific League title since 1981 (his win streak lasted until 14 April of the following season, when it reached 12–0) and contributing to their first championship since 1961 in the Japan Series over the Dragons. Darvish was chosen to take the hill for the first game of each of the Pacific League playoffs, Japan Series, and the 2006 Asia Series (played between the champions of Japan, China, Taiwan, and South Korea at the end of the season). Darvish, then 20 years old, became the first pitcher to start a Japan Series game since 1987 while under the age of 21, and the fifth pitcher in NPB history to win a Japan Series game at that age with his win in Game 5 of the series. He also won the Asia Series Most Valuable Player award.

Prior to the 2006 season Darvish’s “go-to” pitch was a screwball, and he tends to rely more on his off-speed pitches than his fastball. After injuring his shoulder in an exhibition game start against the 2006 World Baseball Classic Japanese national team in February 2006, because of the strain the screwball had gradually been putting on his shoulder, he took the pitch out of his in-game repertoire and worked to develop his splitter until it became an equally effective pitch that would replace the screwball. He also has succeeded in increasing his fastball velocity from year to year.

Darvish made his national team debut in the 2007 Asian Baseball Championship (which also functioned as the Asian qualifying tournament for the 2008 Beijing Olympics) against Chinese Taipei on 3 December 2007. Because Japanese law requires that a person holding dual citizenship choose a single nationality before their twenty-second birthday, Darvish had chosen to retain his Japanese citizenship so that he could play for the national team in the Olympics.

In August 2007, Darvish acknowledged a relationship with Japanese model and actress Saeko. He announced later that Saeko was pregnant with their son. They married on 11 November 2007, and their son was born in March 2008. Their second child, a boy, was born in February 2010. Darvish’s divorce from Saeko was finalized on the same day in January 2012 that he officially signed with the Rangers.

Darvish established a humanitarian fund dedicated to the construction, installation, and maintenance of wells, well pumps, and rainwater storage facilities in developing countries called the “Yu Darvish Water Fund” in February 2007. He announced plans to contribute to the fund by donating 100,000 yen each time he notches a regular season win. The fund is managed by the Japan Water Forum.

In 2008, Darvish was named the Fighters’ starter in the season opener for the second consecutive year, pitching a complete game shutout in that very game (the Fighters won 1–0). Even as his team struggled in the opening months of the season, Darvish continued to rack up wins at a pace that exceeded his own in the previous season. As the year went on, he and Eagles ace Hisashi Iwakuma emerged as the league leaders in both wins and ERA. On 10 April, in their only match-up of the season, neither gave up a single hit through the first five innings. Iwakuma went the distance, throwing just 100 pitches and giving up just one run on three hits; yet Darvish topped this, throwing another complete game shutout on three hits and just 95 pitches in one of the best pitchers’ duels of the season.

Named the ace of the Japanese national team by manager Senichi Hoshino in the 2008 Beijing Olympics, Darvish took the hill in Japan’s first game of the preliminary round against Cuba on 13 August, but was charged with the loss after giving up four runs in 4 innings. The subpar outing caused Hoshino to lose faith in him and scratch Darvish from the semi-finals that he had penciled him in for, sending Darvish to the mound only in situations that would have no bearing on Japan’s fate in the tournament. Darvish started the last game of the preliminary round against the United States on 20 August and was brought in to mop up after the U.S. had taken a decisive lead in the bronze medal match, finishing the tournament 0–1 with a 5.14 ERA (albeit with 10 strikeouts in seven innings pitched).

Darvish started the Fighters’ season opener for the third straight year in 2009, taking the mound against the Eagles on 3 April in a matchup with the reigning Sawamura Award winner and World Baseball Classic teammate Hisashi Iwakuma. Darvish gave up three runs in the first inning but went the distance, allowing no runs from the second inning onward in a 121-pitch, complete game loss (Iwakuma held the Fighters to one run over six innings and was credited with the win). On 24 April, he struck out six straight and 11 overall en route to a four-hit, complete game shutout (his first of the season) over the Buffaloes, following it up by holding the Lions to one run and striking out 11 over nine innings in a no-decision in a match-up with fellow 22-year-old ace Hideaki Wakui on 1 May (the Fighters lost 2–1 in extra innings).

Darvish pitched in the 2009 World Baseball Classic as the de facto ace of the Japanese national team, starting the opening game against China on 5 March. He pitched four innings, allowing one walk and no hits and striking out three as Japan beat China, 4–0. However, pitching in a Major League stadium for the first time in his career, he struggled in his second outing of the tournament against South Korea on 17 March, throwing five innings and giving up three runs (two earned) on four hits and a walk and ultimately being charged with the loss. His first career save would follow six days later, when he pitched the final inning of the semi-finals against the United States, yielding no runs and a single and striking out two as Japan won 9–4.

Darvish’s 2010 season was another strong individual performance, but he struggled to win as many games due to the Fighters troubles. The Fighters finished 74–67, but in fourth place. His opening day loss was reflective of his 2010 season; he pitched well but the team struggled. He began the 2010 season losing to the Fukuoka SoftBank Hawks on 20 March. Darvish allowed two early unearned runs on his way to a complete game loss (5 runs allowed, 3 earned runs) striking out 13. The Fighters began the season with a 5–14–1 stretch that was put them with their worst winning percentage in five years. They struggled in all phases of play, but Darvish continued to pitch well. Even at this low point, he was leading the league in strikeouts even as the rest of the rotation was 3–9. Darvish struck out at least 10 hitters in each of his first five starts.

Darvish’s 2010 season also was noticeable because speculation increased about his potential move (or posting) to Major League Baseball. Darvish was interviewed by The Associated Press where he announced his plans to review his options at the end of the season. He noted, “Right now, I’m just focused on helping my team win this season … Once the season is over, I’ll consider my future.” The Associated Press noted that both his exposure to international play during the 2009 World Baseball Classic and recurring injuries both led him to consider leaving Japan. In addition to back problems he also missed a start in June with a sore right knee.

On 18 October 2010, Darvish posted on his blog that he would be returning to the Fighters for the 2011 season.

On 6 January 2011 Darvish agreed to a contract for the 2011 season that would make him the highest-paid player in Japan. His salary was 500 million Japanese Yen (which on 6 January converted to $6,065,490 US dollars).

The 2011 Nippon Professional Baseball season was delayed by the Tohoku earthquake. Controversy emerged over when baseball should resume. Commissioner Ryozo Kato was criticized for comparing the resumption to the return of Major League Baseball ten days after the 9/11 terrorist attacks. Darvish was among the players who felt it was not appropriate to quickly return to baseball, “I am a baseball player and a human being as well. I cannot think about baseball alone as I normally do.” Darvish took part in efforts to raise funds for the relief efforts and personally donated 50,000,000 Yen (about US$620,000) to the Japanese Red Cross.

Eventually the teams agreed to play the full 144-game schedule, but the start of the season would be pushed back several weeks. The season began on 12 April 2011 and Darvish started against the Saitama Seibu Lions. He struggled, allowing seven runs in seven innings and taking the loss.

On 5 July 2012, the MLB announced that Yu Darvish for the American League and David Freese for the National League were the final two players to make the 2012 MLB All-Star Game rosters. Darvish had 10 wins and five losses with a 3.59 ERA when the MLB announced him as an All-Star. However, Darvish didn’t get a chance to pitch in the game, watching from the dugout as his team lost 8–0.

On 2 April 2013, Darvish pitched a perfect game through eight 2/3 innings against the Houston Astros, before throwing a slider and giving up a single to Marwin González. He threw 111 pitches, striking out 14 and walking none. On 27 May, Darvish became the first player since Randy Johnson and Curt Schilling in 2002 to have 100 strikeouts by Memorial Day. On 10 July 2013, Darvish was placed on the 15-day DL due to a strained trapezius and was replaced on the All-Star roster by Matt Moore. On 12 August 2013, he pitched a no-hitter through seven 1/3 innings against the Houston Astros until giving up a home run to Carlos Corporán. Darvish struck out a career-high of 15 in that game and Texas won 2–1. By season’s end, he compiled 277 strikeouts in just 209 2/3 innings. Additionally, was fourth in the American League in with a 2.83 ERA, behind Aníbal Sánchez, Hisashi Iwakuma, and Bartolo Colón. Despite a pedestrian 13–9 won-lost record, Darvish placed second in the Cy Young voting to the Detroit Tigers’ Max Scherzer.

Darvish, along with Ichiro Suzuki and Daisuke Matsuzaka, chose not to play in the 2013 World Baseball Classic.

In his first start of the 2014 season, Darvish faced the Tampa Bay Rays on 6 April. He struck out David DeJesus and Wil Myers to start the game, notching his 500th career strikeout. The two strikeouts gave Darvish 401 ⁄3 career IP in the Major Leagues, making him the fastest to reach 500 SO in terms of innings pitched. It topped Kerry Wood’s previous record by three innings. The Rangers won the game 3–0 as Darvish pitched seven shutout innings and struck out six overall. On 9 May, Darvish took a no-hitter in the seventh inning against the Boston Red Sox before giving up a single to David Ortiz. The hit was initially ruled an error, thus allowing Darvish to take a no-hitter into the ninth before Ortiz recorded a single in that inning, however Major League Baseball subsequently overruled the scoring decision, ending the no-hitter in the seventh. On 11 June 2014 Darvish threw his first complete game shutout against the Miami Marlins. Darvish allowed 6 hits, 3 walks and struck out 10.

On 6 July 2014 Yu Darvish was elected to play the 2014 MLB All-Star Game. Darvish entered the All Star Game in the third inning to retire all three batters.

During spring training, Darvish began to experience soreness in his right triceps. He underwent an MRI the following day, eventually to reveal that his right elbow had a torn UCL, preventing Darvish from participating for the entire 2015 baseball season. He underwent Tommy John surgery on 17 March 2015, performed by Dr. James Andrews.

Darvish began the 2016 season on the 15-day disabled list in an effort to continue recovery from the Tommy John surgery he underwent in 2015. He returned on 28 May against the Pittsburgh Pirates, pitching 5 innings with 7 strikeouts and one run allowed on 3 hits as the Rangers went on to win 5–2. On 13 June 2016, he was placed on the 15-day disabled list due to neck and shoulder strains. On 24 August 2016, he hit his 1st career MLB home run in an away game against the Cincinnati Reds, the first home run by a Rangers pitcher since Bobby Witt in 1997.

On 30 July 2015, Darvish announced that his girlfriend, former world-champion wrestler Seiko Yamamoto, gave birth to their son on 29 July.

On 31 July 2017, the Rangers traded Darvish to the Los Angeles Dodgers for prospects Willie Calhoun, A. J. Alexy, and Brendon Davis. He was 4–3 with a 3.44 ERA in nine starts for the Dodgers. Overall in 2017, combined with both teams, Darvish made 31 starts with a 10–12 record, 209 strikeouts, 12 wild pitches (7th in the major leagues), and a 3.86 ERA.

In the post-season, he won his one start in the 2017 NLDS, allowing one run in five innings against the Arizona Diamondbacks while striking out seven. He also pitched well in the 2017 NLCS against the Chicago Cubs, with one run in 6⁄3 innings with also seven strikeouts.

In the 2017 World Series he failed to get out of the second inning in either of his two starts against the Houston Astros. He lost both games, including game seven, and allowed nine runs (eight earned) in 3⁄3 innings while failing to strike out a single batter. They were the shortest two starts of his career. and he became the first starting pitcher since Art Ditmar in 1960 to have two starts of less than two innings in the World Series. Shortly after the World Series, an unnamed Astros player suggested that Darvish had been tipping his pitches. Dodgers teammate Chase Utley had evaluated Darvish’s game three start and concluded that this was not the case, though Darvish changed his approach for game seven. More than a month later, a Sports Illustrated article revealed that the Astros had figured out how Darvish was tipping his pitches: “Darvish holds the ball at his side when he gets the sign from the catcher. Whether he re-grips or not as he brings the ball into his glove was the tip-off whether he was going to throw a slider/cutter or a fastball.” This unnamed Astros player said the Astros had known about this going into Game 3 which they also won, but that they had an even better game plan for Game 7.

On February 13, 2018, Darvish signed a six-year, $126 million contract with the Chicago Cubs. He played his first game with the Cubs on 31 March 2018, against the Miami Marlins. He allowed 5 runs in 4.1 innings as the Cubs won 10–6 in 10 innings. On 7 May, Darvish was placed on the 10-day disabled list due to the flu. On 26 May, Darvish was again placed on the 10-day disabled list due to right triceps tendinitis. On 19 August 2018, Darvish began a rehab stint. While warming up before the second inning, Darvish summoned trainers and was removed from the game. An MRI revealed Darvish had a stress reaction on his right elbow as well as a triceps strain, ending his 2018 season, after only 8 games and 40 innings pitched, in which he was 1-3 with a 4.95 ERA.

Darvish in 2019 for the Cubs was 6–8 with a 3.98 ERA and 225 strikeouts in 31 starts. He gave up 33 home runs, the most in the National League, threw 11 wild pitches, the second-most in the NL, and hit 11 batsmen, third-most in the league.

Darvish is a right-handed pitcher who throws from a three-quarter arm slot in a drop-and-drive motion. He has a large frame for a pitcher, listed at 6 ft 5 in and 220 lb. Darvish throws a four-seam fastball which averages 93–95 mph (tops out at 99 mph), as well as a hard slurve (slider) in the low 80s with a sharp break. He complements these two with a wide repertoire of secondary pitches, including a two-seam fastball (also described as a shuuto), a cutter, two curveballs, a splitter, and an occasional changeup. Darvish has a “fast curve” and a “slow curve”, the former averaging about 80 mph and the latter about 71. The slow curve is almost exclusively used in no-strike and 1-strike counts, while the fast curve is mostly used in 2-strike counts. Some professional scouts consider Darvish to have the best repertoire of quality pitches, including the best slider, in all of Major League Baseball. In August 2019, Darvish learned a knuckle curve from Cubs teammate Craig Kimbrel and began using the pitch.

In 2019 season alone, he used 10 different pitches: Cutter with two different movements, four seam and two seam fastballs, slider, splitter, normal and slow curveballs, knuckle curve and a changeup. In 2020, he revealed on Twitter that he learnt a ‘supreme pitch’, which is a hybrid between a splitter and two-seam fastball. This pitch can reach 93 mph.

Darvish resides in a $4.55 million home in Evanston, Illinois. Darvish has caused controversy in his neighborhood with requests to construct a six-foot high fence around the property and to acquire adjacent land owned by the City of Evanston. The six-foot fence would require a zoning variance and would obstruct the lake views of neighbors. Darvish built a 6-foot solid wood fence, and Darvish’s neighbors filed a lawsuit in Cook County Circuit Court on March 29, 2019, asking a judge to rule that the Darvishes’ fence obstructed their view of Lake Michigan, violating an easement and a verbal agreement.

With the Astros being disciplined on 13 January 2020 for using cameras to steal catcher-to-pitcher signals during the 2017 MLB postseaon, Darvish refused to blame sign stealing for his poor starts and instead suggested that the 2017 Astros batters were talented, and humorously joking on Twitter that he would wear a “Yu Garbage” jersey if the Dodgers held a championship parade.