May 29 – Mike Schmidt of the Philadelphia Phillies calls a press conference and tearfully announces his retirement, effective immediately. Nonetheless, he will be voted to start the All-Star Game, and is permitted to appear in uniform.
June 3 – At the Astrodome, the Houston Astros and Los Angeles Dodgers engage in a 22-inning battle lasting seven hours and fourteen minutes, setting a new record for the longest night game in National League history. Houston's ace pitcher Mike Scott, never known for his batting abilities, surprises everyone by coming through with a walk-off sacrifice fly to give the Astros a 5–4 victory. Amazingly, the two teams meet again just hours later and wage another marathon, with Houston once again emerging victorious, 7–6 in 13 innings.
August 15 – San Francisco Giants pitcher Dave Dravecky, making a comeback from cancer in his deltoid muscle, snaps his humerus bone while throwing a pitch to Tim Raines in the sixth inning of a game against the Montreal Expos. The bone had been frozen as part of surgery for his cancer the previous year. Dravecky's cancer would return after the Giants' pennant win, forcing his retirement and the eventual amputation of his arm.
August 24 – Commissioner A. Bartlett Giamatti announces in a press conference that Pete Rose is banned from baseball for life, in the wake of evidence that has come to light regarding Rose's gambling history.
October 3 – Kirby Puckett wins an unlikely (at the time) American League batting title, taking advantage of an off-year by Boston's Wade Boggs due to marital issues. Puckett clinches the title in Seattle on a double in the final game of the season, finishing with a final average of .339.
October 9 – After 43 years on the air, NBC concludes its run as the #1 over-the-air television broadcaster for Major League Baseball games. Game 5 of the NLCS between the San Francisco Giants and Chicago Cubs is the final baseball broadcast shown on the network.
October 17 – Game 3 of the World Series is postponed due to the Loma Prieta earthquake, which struck immediately before the game was set to begin. It would be rescheduled for ten days later, October 27.
January 9 – Bill Terry, 90, Hall of Fame first baseman for the New York Giants who batted .341 lifetime and was the last National Leaguer to hit .400 (.401 in 1930); also managed Giants to 1933 World Series title
January 21 – Carl Furillo, 66, All-Star right fielder for the Dodgers who batted .300 five times and won 1953 batting title
January 22 – Willie Wells, 83, All-Star shortstop of the Negro Leagues who combined batting power with excellent defense
January 23 – George Case, 73, All-Star outfielder for the Washington Senators who led the AL in stolen bases six times
February 17 – Lefty Gómez, 80, Hall of Fame pitcher for the New York Yankees who had four 20-win seasons and a .649 career winning percentage; led AL in strikeouts three times and in wins and ERA twice each, and was 6–0 in World Series
April 8 – Bus Saidt, 68, sportswriter who covered the Phillies, Mets and Yankees for the Trenton Times since 1967; previously a minor league broadcaster
April 16 – Jocko Conlan, 89, Hall of Fame umpire who worked in the National League from 1941 to 1964, including five World Series and six All-Star Games
May 17 – Specs Toporcer, 90, infielder for the Cardinals for eight seasons, and the first non-pitcher to wear eyeglasses; later a minor league manager
June 8 – Bibb Falk, 90, left fielder who batted .314 with White Sox and Indians; coached Texas to two College World Series titles
June 8 – Emil Verban, 73, All-Star second baseman for four NL teams who hit .412 in the 1944 World Series
June 15 – Judy Johnson, 89, Hall of Fame third baseman of the Negro Leagues who became the major leagues' first black coach, and later a scout
July 18 – Donnie Moore, 35, All-Star relief pitcher who never overcame the disappointment from giving up a pivotal home run in the 1986 ALCS
August 17 – Fred Frankhouse, 85, All-Star pitcher for the Cardinals, Braves and Dodgers who ended Carl Hubbell's 24-game winning streak in 1937
August 30 – Joe Collins, 66, first baseman for the New York Yankees who hit four World Series homers
September 1 – A. Bartlett Giamatti, 51, commissioner of baseball since April, previously NL president since 1986, known for numerous writings on the sport as well as his banishment of Pete Rose