A total of 67 Japanese-born^[1][2] players have played in at least one Major League Baseball (MLB) game. Of these players, eight are on existing MLB rosters. The first instance of a Japanese player playing in MLB occurred in 1964, when the Nankai Hawks, a Nippon Professional Baseball (NPB) team, sent three exchange prospects to the United States to gain experience in MLB's minor league system. One of the players, pitcher Masanori Murakami, was named the California League Rookie of the Year while playing for the Fresno Giants (the San Francisco Giants' Class-A team). Giants executives were impressed with his talent and on September 1, 1964, Murakami was promoted, thus becoming the first Japanese player to play in MLB, as well as being the first Asian player.^[3] After Murakami put up good pitching statistics as a reliever, Giants executives sought to exercise a clause in their contract with the Hawks that, they claimed, allowed them to buy up an exchange prospect's contract. NPB officials objected, stating that they had no intention of selling Murakami's contract to the Giants and telling them that Murakami was merely on loan for the 1964 season. After a two-month stalemate the Giants eventually agreed to send Murakami back to the Hawks after the 1965 season. This affair led to the 1967 United States – Japanese Player Contract Agreement, also known as the "Working Agreement", between MLB and NPB, which was basically a hands-off policy.^[4][5]

For thirty years Murakami was the only Japanese player to appear in an MLB game. Pitcher Hideo Nomo, with the help of agent Don Nomura, became the second Japanese player to play in MLB in 1995. Nomo, who was not yet eligible for free agency in Japan, was advised by Nomura that a "voluntary retirement" clause in the Working Agreement did not specify that a player wishing to play again after retiring must return to NPB. Nomo utilized this loophole to void his NPB contract with the Kintetsu Buffaloes and play in MLB. He announced his retirement from NPB in late 1994 and signed with the Los Angeles Dodgers in February 1995.^[6] Nomo's maneuver and Hideki Irabu's later MLB contractual complications were contributing factors to a major revision of the Working Agreement in 1998 that created the posting system.^[7] Since its inception 22 Japanese players have been signed through the system, however one of these players, Shinji Mori, did not play in a single MLB game due to an injury. NPB players who have nine or more years of playing service with NPB can become international free agents and do not need to enter MLB through the posting system.^[8] The remaining Japanese players that have played in MLB have either signed as free agents or signed as amateur players. Mac Suzuki, Kazuhito Tadano, and Junichi Tazawa are the only Japanese players to have debuted in MLB without previously playing in NPB.^[9][10][11] All 30 MLB teams have had at least one Japanese player on their roster.

Japanese players have had a range of success in MLB. Twelve players have been selected to participate in the All-Star Game; Ichiro Suzuki has made the most appearances with ten. In addition to these selections, Ichiro has won several prestigious MLB awards including the American League (AL) Rookie of the Year Award and the AL Most Valuable Player (MVP) Award in 2001, the All-Star Game MVP Award in 2007 and multiple Gold Glove and Silver Slugger Awards. Ichiro also holds the MLB record for the recording the most hits in a single season. Hideo Nomo was the only Japanese pitcher to throw a no-hitter until Hisashi Iwakuma accomplished the feat on August 12, 2015. Nomo threw two in total; the first came in 1996 and the last occurred in 2001.

Currently, Shohei Ohtani is the only player in MLB history to win the AL Most Valuable Player (MVP) Award twice unanimously in 2021 and 2023, the first player in MLB history with 10 wins and 40 home runs in a season,^[12] and the first player in MLB history to be named to both first teams for the 2023 All-MLB Team in the same season (as a designated hitter and starting pitcher respectively).^[13] Ohtani is also the first Japanese-born player to hit for the cycle, the first Japanese-born player to win a major league home run title, leading the American League with 44 home runs^[14] the first Japanese-born player to win the AL Hank Aaron Award,^[15] and the first Japanese player to have the most popular Major League Baseball jersey sales.^[16] In addition, Ohtani has also won the American League (AL) Rookie of the Year Award in 2018, two Silver Slugger Awards, and multiple Edgar Martínez Outstanding Designated Hitter Awards.^[17] Ohtani also signed the largest contract in professional sports history, a 10-year $700 million contract with the Los Angeles Dodgers.^[18] while Yoshinobu Yamamoto received the most guaranteed dollars ever given to a pitcher, signing a 12-year, $325 million contract with the Dodgers.^[19]

Thirteen Japanese players have played in the World Series. Of these players, So Taguchi has won the most with two and Hideki Matsui is the only one to win the World Series MVP Award. The 2007 World Series had the most Japanese players, with Daisuke Matsuzaka and Hideki Okajima pitching for the Boston Red Sox, and Kazuo Matsui playing for the Colorado Rockies.

* Games played through the 2023 regular season.

Bold indicates the player was selected to the starting roster

Bold indicates that the team won the World Series that year