Kawasaki earned the starting shortstop job for the Hawks’ nigun team (Japanese for “minor league” or “farm team”) in his rookie season (2000), hitting .300 and finishing fifth in the Western League in batting average that year. In 2001, his second season in the pros, he came second (to only then-Tohoku Rakuten Golden Eagles outfielder Akihito Moritani) with 29 stolen bases. He made his debut at the ichigun (major league) level on October 3 against the Orix BlueWave as the starting shortstop and No. 2 hitter, but went hitless in four at-bats that year.

In 2003, Kawasaki started in the Hawks’ season opener for the first time in his career because of injuries to veteran Yusuke Torigoe, starting at shortstop as the team’s No. 2 hitter. After Torigoe returned to the lineup, Kawasaki moved over to third base, wreaking havoc on the basepaths along with leadoff hitter Arihito Muramatsu and Iguchi (who sat in the 3-hole). He hit his first career home run on July 28 off Buffaloes right-hander Ken Kadokura, and while he finished the season just short of .300, he played his first full season at the ichigun level and hit .294 with two homers, 51 RBI and 30 steals, playing a key role in the Hawks’ league title and eventual Japan Series championship.

While Kawasaki is considered by many to be a great base stealer, having led the league in steals in 2004 with 42, his career stolen base percentage is 70.0 percent (as of May 13, 2009). Modern sabermetric theory suggests that a player needs to be successful 70 to 75 percent of the time in stealing bases to have any kind of positive effect on the team’s run production.

Kawasaki had a somewhat disappointing season in 2005, seeing his batting average drop off from .303 in 2004 to .271 and his on-base percentage from .359 to just .326, knocking in just 36 runs and stealing only 21 bases. Despite this, he was named to the Japanese national team to play in the inaugural World Baseball Classic during the off-season.

Coming off a championship in the inaugural World Baseball Classic, Kawasaki bounced back in 2006, hitting a career-high .312 and winning the Pacific League Best Nine and Golden Glove awards at shortstop (each for the second time). He also received the most fan votes at shortstop for the MLB Japan All-Star Series held in November, but withdrew from the tournament after injuring the ring finger on his right hand during Fall Training.

Kawasaki suffered various injuries in the 2007 season, twice spending time in the minors to rehab and playing just 95 games (though he hit .329 and slugged .428, both career highs).

Kawasaki’s woes continued into 2008 as he attempted to play through an injury to his left foot. He hit a team-high .366 in interleague games and collected 37 hits (leading the NPB), leading the Hawks to their first interleague title and winning the interleague Most Valuable Player (marking the first time a position player had been named to the award). However, though he was chosen to play in the 2008 Beijing Olympics as a member of the national team, he was diagnosed with periostitis during the tournament. On August 25, Kawasaki was found to have a stress fracture in his second metatarsal bone upon returning to Japan after the Olympics. He made an earlier-than-expected return, coming off the bench in the last game of the regular season (and then-manager Sadaharu Oh’s last at the helm) on October 7 against the Eagles, but finished 0-for-2 with an intentional walk (the Hawks lost the game in extra innings).

In 2008, Kawasaki was chosen to play in the Olympics for the first time as a member of the national team, but ended up playing in just three games (though he went 4-for-7 and scored two runs) due to a nagging left foot injury. Japan came up short in their medal run, finishing fourth behind South Korea, Cuba and the United States.

Kawasaki played in the World Baseball Classic as a member of the national team for the second time in 2009. While he played in just five games and saw only seven at-bats (mostly as a pinch hitter) due to manager Tatsunori Hara’s decision to use Saitama Seibu Lions second baseman Yasuyuki Kataoka over Kawasaki against left-handed starting pitchers, Kawasaki was instrumental in Japan’s win over the United States in the tournament semi-finals, starting at third base as Japan’s No. 9 hitter and going 2-for-4 with a steal and an RBI.

In his professional American debut, on March 2, 2012, Kawasaki went 0–3 against the Oakland Athletics, with two strikeouts, starting at shortstop. He was replaced in the sixth inning by Carlos Triunfel.

On October 24, 2012, the Mariners announced they had released Kawasaki. He hit .192/.257/.202 in 115 plate appearances in 61 games.

Kawasaki agreed to a minor league deal with the Toronto Blue Jays on March 14, 2013. He started the 2013 season on the roster of the Triple-A Buffalo Bisons. Kawasaki was called up to the Blue Jays on April 13 when José Reyes was added to the disabled list. With his appearance for the Blue Jays on April 13, Kawasaki became the first Japanese-born position player to appear in a game for Toronto.

On April 21, 2013, Kawasaki batted in the leadoff slot for the first time in Toronto, scoring the game’s first run against the New York Yankees. On May 26, in the final game of a 4-game series against the Baltimore Orioles, Kawasaki recorded his first MLB walk-off hit, with a 2 run double against Baltimore closer Jim Johnson. On June 21, Kawasaki hit his first MLB home run, a two-run shot off Baltimore reliever Tommy Hunter, which tied the game 6–6. The Blue Jays would win the game 7–6 to extend their winning streak to 9 games. Kawasaki, at 32 years of age, became the oldest player in Blue Jays’ history to hit his first career home run, one year older than Ken Huckaby. Kawasaki was optioned back to Triple-A Buffalo on June 26 when Jose Reyes was activated from the disabled list.

Toronto recalled Kawasaki from Triple-A Buffalo on June 28 after left-fielder Melky Cabrera was placed on the 15-day disabled list with left knee tendonitis. Kawasaki made his first MLB start at second base in a game against the Boston Red Sox on June 30, 2013. Kawasaki was optioned back to Triple-A on July 13 to make room for Brett Lawrie. Kawasaki was recalled on August 14 after Colby Rasmus was placed on the disabled list. Kawasaki was ejected for the first time in his major league career on September 21, against the Boston Red Sox after being called out at first base by umpire Eric Cooper and then subsequently throwing his helmet to the ground. He recorded his first career 4-hit game on September 25, against the Baltimore Orioles. Kawasaki finished the 2013 regular season with a .229 batting average, 1 home run, and 24 RBI in 96 games. The Blue Jays declined his $1 million contract option on October 31, making him a free agent. Kawasaki was awarded the GIBBY award for Topic of the Year on December 10, 2013, for his postgame speech on May 26.

On December 24, 2013, it was announced that Kawasaki had signed a minor-league contract with the Blue Jays that included an invitation to spring training. He did not make the major league squad, and was assigned to Triple-A Buffalo. On April 13, Kawasaki was recalled when Maicer Izturis was placed on the disabled list. He was optioned back to Buffalo on April 19, when Jose Reyes was activated. He was recalled again on June 17 when Steve Delabar was optioned to Buffalo. Kawasaki saw regular playing time after his call-up and appeared in 82 games for the Blue Jays in 2014. He batted .258 with 17 RBI for the season. Kawasaki was sent outright to the Buffalo Bisons on October 1, 2014, and became a free agent on October 31.

Kawasaki’s first son, Issho, was born on August 16, 2013, in Toronto.

The Blue Jays re-signed Kawasaki to a minor league contract with an invitation to spring training on January 16, 2015. On March 31, he was reassigned to minor league spring training. The Blue Jays purchased Kawasaki’s contract from Buffalo on May 21, and optioned him back to Buffalo on May 25 when José Reyes returned from the disabled list. He was recalled on May 31 when Steve Tolleson was placed on the disabled list, and optioned back on June 10. On August 1, Kawasaki was recalled from Buffalo. He was optioned back to Buffalo on August 9 when Cliff Pennington was added to the Blue Jays’ roster. On September 1, Kawasaki was recalled by the Blue Jays. He appeared in 23 games in 2015, and batted .214 with 2 RBI. Though Kawasaki did not play in the Postseason, he was invited to travel with the team and was present for every Postseason game in the Blue Jays’ dugout. He became a free agent at the end of the season.

On January 21, 2016, Kawasaki signed a minor league contract with the Chicago Cubs that included an invitation to spring training. He was released on March 29, and re-signed to another minor league contract later that day. On April 3, he was added to the 40-man roster and optioned to the Triple-A Iowa Cubs. He was recalled to the 25 man roster on April 8 when Kyle Schwarber was placed on the disabled list. He was optioned back to Iowa on April 15, when Javier Báez was activated from the disabled list. He was recalled on July 9, and optioned back to Iowa on July 15. On September 6, Kawasaki was recalled from Iowa. In 14 games of 2016, Kawasaki batted .333 with an RBI and two stolen bases. The Cubs finished the season with a 103-58 record for an NL Central pennant, and would eventually win the 2016 World Series, ending their 108-year long world champion title drought. Kawasaki was ineligible for post-season play in 2016, but traveled with the Cubs throughout the playoffs and joined the team on the field for the post-game celebrations.

On January 7, 2017, Kawasaki signed a new minor league contract with the Cubs. He was released on March 28.

On March 31, 2017, Kawasaki signed with the Fukuoka SoftBank Hawks. He won his fourth Japan Series with the Hawks in 2017. On March 26, 2018, Kawasaki was released by the Hawks, and reportedly intended to retire. However, he clarified his statement later that day, announcing that he was temporarily stepping away from baseball due to a nerve disorder.

On July 9, 2019, Kawasaki became a guest coach for the Wei Chuan Dragons of the Chinese Professional Baseball League (CPBL). On July 13, 2019, he became player-coach.

On September 7, 2020, Kawasaki signed with the Tochigi Golden Braves of the Baseball Challenge League. On September 13, 2020, he hit a home run on the first pitch he saw in his debut.