- March 20 - Leo Durocher, hired to manage the Yokohama Taiyō Whales of the Japanese League, is sick with hepatitis and asks for a five-week delay in reporting. Durocher receives a telegram from the Whales stating: "Since the championship starts in 20 days, it's better if you stay home and take care of yourself for the remainder of the season."
- March 26 - The American League approves the purchase of the new Toronto franchise by the LaBatt's Brewing Company for $7 million.
- April 21 - At Wrigley Field, Tim Foli of the Montreal Expos hits for the cycle, but it takes him two days to do it. Foli has a single, double and triple against the Cubs, but with the Expos ahead 11–3, the game is suspended on account of darkness. When play resumes the next day, Foli will add a home run in the 8th inning.
- May 15 - Mark Fidrych wins his first major league start, a complete game two-hit 2–1 victory over the Cleveland Indians. Fidrych holds the Indians hitless for six innings, talks to the ball, and tamps down the mound before toeing the rubber each inning.
- June 25 - The Texas Rangers' Toby Harrah becomes the only shortstop in major league history to go through an entire doubleheader without a fielding chance. At bat, Harrah makes up for the inactivity, collecting six hits including a grand slam in the opener, and another home run in game 2. The Rangers beat the Chicago White Sox in the first game 8–4, but lose the nightcap 14–9.
- September 6 - Dodgers catcher Steve Yeager is seriously injured when the jagged end of a broken bat strikes him in the throat while he is waiting in the on-deck circle.
- October 14 - In Game 5 of the American League Championship Series, the New York Yankees take a 6-3 lead before Kansas City's George Brett connects for a 3-run home run. In the bottom of the 9th, New York's Chris Chambliss smashes the first pitch off Kansas City's Mark Littell into the right field stands for a 7-6 win, and the Yankees' first World Series appearance since 1964.
- October 21 - In the World Series, the Cincinnati Reds beat the New York Yankees 7-2, completing a four-game sweep. Series MVP Johnny Bench has two home runs and five RBI in the Series, and demolishes the Yankees with .533 hitting. Opposing catcher Thurman Munson had six straight singles to tie a World Series mark. The Reds become the first team since the 1969 playoff expansion to go through an entire postseason without a defeat.
- March 11 - Larry Gardner, 89, third baseman for three Red Sox champions who batted .300 five times; longtime coach at University of Vermont
- April 9 - Francisco Barrios, 28, Chicago White Sox pitcher who combined with Blue Moon Odom to no-hit Oakland in 1976
- April 15 - George Scales, 75, second baseman in the Negro Leagues, also a manager in the Puerto Rican winter league
- May 2 - Dan Bankhead, 55, first black pitcher in major league history (Brooklyn Dodgers, 1947, 1950-51); also homered in first major league at-bat
- May 30 - Max Carey, 86, Hall of Fame center fielder, mainly with the Pittsburgh Pirates, who led NL in steals ten times, holding league career record of 738 until 1974; set NL records for career games, putouts, chances and double plays in outfield, and batted .458 in 1925 World Series
- June 11 - Jim Konstanty, 59, All-Star pitcher who became the first reliever to win the MVP award, with the 1950 "Whiz Kid" Phillies
- June 15 - Jimmy Dykes, 79, All-Star third baseman for the Athletics and White Sox who went on to become the winningest manager in White Sox history; also managed five other teams
- June 23 - Lon Warneke, 67, 5-time All-Star pitcher had three 20-win seasons for Cubs, led NL in wins and ERA in 1932; later an NL umpire for seven years
- June 30 - Firpo Marberry, 77, pitcher for the Washington Senators who established single-season and career records for both saves and relief appearances, led majors in saves a record five times; also 94-52 as a starter
- July 9 - Tom Yawkey, 73, owner and president of the Boston Red Sox since 1933, and vice president of the American League from 1956 to 1973
- July 21 - Earle Combs, 77, Hall of Fame center fielder for the New York Yankees who batted .325 lifetime and led the AL in triples three times; batting leadoff, he had eight seasons of 100 runs, and batted .350 over four World Series
- September 25 - Red Faber, 88, Hall of Fame pitcher who played his entire 20-year career with the Chicago White Sox, winning 254 games and leading AL in ERA twice; his four 20-win seasons included a 25-win campaign for the scandal-decimated 1921 team, which finished 62-92
- October 9 - Bob Moose, 29, pitcher for the Pittsburgh Pirates since 1967, threw no-hitter in 14-3 season in 1969
- December 1 - George Earnshaw, 76, pitcher who had three 20-win seasons for 1929-30-31 AL champion Athletics; later a scout and coach
- December 2 - Danny Murtaugh, 59, manager who in four stints with the Pittsburgh Pirates won two World Series (1960, 1971) and three division titles; led NL in steals as rookie in 1941
- December 7 - Duke Maas, 47, pitcher who won 45 games for the Tigers, Athletics and Yankees
- December 9 - Wes Ferrell, 68, All-Star pitcher who had six 20-win seasons for the Indians and Red Sox, 193 career wins included a no-hitter; also a career .280 hitter, and caught by brother Rick for five seasons
- December 10 - Danny Thompson, 29, infielder, mainly with the Minnesota Twins, who played four seasons after being diagnosed with leukemia