1972 was tainted by a players' strike over pension and salary arbitration. The strike erased the first week and a half of the season, and the Leagues decided to just excise the lost portion of the season with no makeups. As a result, an uneven number of games were cancelled for each team; some as few as six, some as many as nine. The lack of makeups of those games, even when they affected playoffs, led to the Boston Red Sox losing the American League East by half a game to the Detroit Tigers.
1972 marked the first year for the Texas Rangers, who had moved to Arlington from Washington, D.C. (where they played as the Washington Senators), after the 1971 season. There would be no baseball in D.C. until 2005. The team was one of the worst ever fielded by the franchise, losing 100 games for the first time since 1964. Manager Ted Williams hated living in the Dallas-Fort Worth area, and resigned at the end of the season.
April 1 – 13 – The first players' strike in baseball history wipes 6–8 games off the schedule of each MLB team. It is agreed that those games will be canceled (i.e., not even played to resolve pennant races). This results in teams not being scheduled for the same number of games in the 1972 season; the schedule imbalance would lead to the Detroit Tigers edging the Boston Red Sox by only one-half game to win the American League East Division championship. The strike results in the team owners adding salary arbitration to the collective bargaining agreement, and increasing pension fund payments.
May 14 – In front of a Mother's Day crowd of 35,000 in New York's Shea Stadium, Willie Mays makes a triumphant return to New York with the Mets, hitting a game-winning home run against his old teammates (the Giants). He scores in the 1st inning on Rusty Staub's grand slam and his solo homer in the 5th inning snaps a 4–4 tie. The final score: Mets 5, Giants 4.
June 24 – In the first game of a doubleheader between the visiting Auburn Phillies and Geneva Senators of the Class A New York-Pennsylvania League, Bernice Gera becomes the first woman to umpire a professional baseball game. She resigns between games after being verbally abused by some spectators and by some involved in the game.
July 11 – At Oakland, Boston's Marty Pattin has his no-hit bid foiled when Reggie Jackson hits a 1-out single in the 9th inning. Boston wins 4–0.
July 14 – In a game between the Detroit Tigers and Kansas City Royals in Kansas City, the Tigers' catcher, Tom Haller, has his older brother Bill Haller right over his shoulder; the first time brothers have served as catcher and home plate umpire in the same Major League game. The Royals win 1–0.
July 18 – Against the Philadelphia Phillies at San Diego Stadium, San Diego Padre pitcher Steve Arlin has a no-hitter broken up with two out in the ninth by a Denny Doyle single. With two strikes on him, Doyle takes advantage of Padre manager Don Zimmer's decision to play third baseman Dave Roberts in by slapping a ground ball that bounces over Roberts' head—a ball that Roberts could have fielded at normal depth. Doyle later advances to second on a balk, then scores on a Tommy Hutton single. Arlin then retires Greg Luzinski on a fly ball to come away with a two-hitter (one of three he pitches on the season; he also hurls two one-hitters during a season in which he finishes 10–21) in a 5–1 Padre victory. To date, no Padre pitcher has hurled a no-hitter; this is the closest any has come to one.
August 29 – Jim Barr of the San Francisco Giants retires the first twenty batters in today's game. Added to the last twenty one batters he retired in his previous game, it establishes a record for consecutive batters retired. It will be tied in 2007 by relief pitcher Bobby Jenks.
September 30 – During the Pirates' 5–0 win over the Mets at Pittsburgh's Three Rivers Stadium, Roberto Clemente hits a double off New York's Jon Matlack in the 4th inning to get his 3,000th and final regular season hit in the major leagues.
October 2 – In the first game of a doubleheader at Jarry Park, Bill Stoneman of the Montreal Exposno-hits the New York Mets 7–0. The no-hitter is 1) the second of Stoneman's career (the first having come on April 17, 1969—only nine games into the Expos' existence), 2) the first no-hitter ever pitched in a regular season game in Canada, and 3) the latest, calendar-wise, that a regular-season no-hitter has been pitched, tied with Addie Joss' perfect game in 1908.
October 8 – The Oakland Athletics won Game 2 of the 1972 American League Championship Series 6–0 win over the Detroit Tigers. A key moment from that game occurred when Oakland's Bert Campaneris who was having a great series hurled his bat at Detroit Tiger pitcher Lerrin LaGrow. Campaneris was fined and suspended for the rest of the series.
October 11 – The Pittsburgh Pirates carry a lead into the bottom of the ninth of the final game of the NLCS. The Reds'Johnny Bench homers to tie the game. After some runners reach base, the Pirates' pitcher, Bob Moose, unleashes a wild pitch, permitting the pennant clinching run to score.
December 10 – The American League votes unanimously to adopt the designated hitter rule on a three-year experimental basis. The DH will replace the pitcher in the lineup unless otherwise noted before the start of the game. In the December 1975 meeting, the AL will vote to permanently adopt the DH. The National League declines to follow suit.
January 2 – Glenn Crawford, 58, outfielder for the St. Louis Cardinals and Philadelphia Phillies in the 1940s
January 21 – Dick Loftus, 70, outfielder for the Brooklyn Robins from 1924–25
February 9 – Chico Ruiz, 33, infielder for the Cincinnati Reds and California Angels
February 28 – Dizzy Trout, 56, All-Star pitcher for the Detroit Tigers who led the AL in wins in 1943 and was MVP runnerup the following year
March 11 – Zack Wheat, 83, Hall of Fame left fielder for the Brooklyn Dodgers who held team career records for games, hits, doubles and triples, a lifetime .317 hitter who retired with the 10th-most hits in history
March 16 – Pie Traynor, 72, Hall of Fame third baseman for the Pittsburgh Pirates who batted .320 lifetime and established a record for career games at third base; was named the best ever at his position in 1969
March 19 – Gordie Hinkle, 66, catcher for the 1934 Boston Red Sox
March 28 – Donie Bush, 84, shortstop of the Detroit Tigers for 14 seasons who led AL in walks five times and was a superlative bunter; later managed Pittsburgh to the 1927 NL pennant
March 30 – Davy Jones, 91, outfielder with the Detroit Tigers who organized a 1912 walkout to protest Ty Cobb's suspension for attacking a heckler
April 2 – Gil Hodges, 47, 8-time All-Star first baseman for the Brooklyn and Los Angeles Dodgers who drove in more runs than any other player during the 1950s and managed the "Miracle Mets" to the 1969 World Series title
April 3 – Alvin Crowder, 73, pitcher who had three 20-win seasons with the Browns and Senators, known for his mastery against the Yankees
May 15 – John Milligan, 68, pitcher who played from 1928 through 1934 for the Philadelphia Phillies and Washington Senators
May 20 – Hoge Workman, 72, pitcher for the 1924 Boston Red Sox, who also played and coached for Cleveland teams of the National Football League
May 22 – Dick Fowler, 51, Canadian pitcher who won 66 games with the Philadelphia Athletics, including a no-hitter
May 24 – Bill Moore, 68, catcher for the 1927 Boston Red Sox
July 31 – Rollie Hemsley, 65, All-Star catcher for seven teams, later a coach and minor league manager
August 13 – George Weiss, 77, executive who solidified the New York Yankees dynasty as the club's farm director and general manager from 1932 to 1960, then became the Mets' first team president
August 24 – J. Roy Stockton, 79, St. Louis sportswriter from the 1910s to the 1950s, also a sportscaster and author of books on baseball
September 2 – Jim Brillheart, 68, who pitched for the Senators, Cubs and Red Sox, and one of the few pitchers in baseball history to appear in over 1,000 games
August 29 – Clem Hausmann, 53, pitcher for the Boston Red Sox and Philadelphia Athletics between 1944 and 1949
September 6 – Charlie Berry, 69, American League catcher for eleven seasons, later an AL umpire from 1942 to 1962 who worked in five World Series and five All-Star Games; also played in the NFL and officiated numerous NFL Championship Games
September 16 – Eddie Waitkus, 53, All-Star first baseman who was shot in 1949 by a teenaged female admirer who lured him to her hotel room
October 9 – Dave Bancroft, 81, Hall of Fame shortstop for four NL teams, known for his defensive skill and also batting over .300 five times; captain of the New York Giants' pennant winners from 1921–1923
October 19 - Butch Glass, 74 pitcher in the Negro Leagues from 1923 to 1930
October 24 – Jackie Robinson, 53, Hall of Fame second baseman for the Brooklyn Dodgers who broke baseball's color line in 1947 after starring in the Negro Leagues; he became the NL's 1949 MVP and batted .311 in a 10-year major league career
November 2 – Freddy Parent, 96, shortstop in the Red Sox' first seven seasons, and the last surviving participant of the inaugural 1903 World Series
November 26 – Wendell Smith, 58, sportswriter for Pittsburgh and Chicago newspapers since 1937 who became the BBWAA's first black member and helped ease Jackie Robinson's entry into the major leagues; also a Chicago sportscaster since 1964
December 20 – Gabby Hartnett, 72, Hall of Fame catcher for the Chicago Cubs who virtually clinched the 1938 pennant with a home run, he established career records for games and home runs as a catcher and was the NL's 1935 MVP
December 31 – Roberto Clemente, 38, right fielder for the Pittsburgh Pirates since 1955; a lifetime .317 hitter, 12-time All-Star and winner of 12 Gold Gloves who was a 4-time batting champion and the NL's 1966 MVP, he collected his 3000th base hit in September