June 2 - After losing five in a row, New York Yankees manager Miller Huggins "shakes up" the slumping lineup by replacing first basemanWally Pipp in the starting lineup with Lou Gehrig, and second basemanAaron Ward with utilityinfielderHowie Shanks. The strategy works as Gehrig goes three-for-five with a run scored, and Shanks goes one-for-four with a run scored in the Yankees' 8-5 victory over the Washington Senators. Pipp only logs seventeen more plate appearances for the rest of the season, and is sold to the Cincinnati Reds for $7,500 following the season.
July 23 - Yankees first baseman Lou Gehrig hits the first of his major league record 23 grand slams to beat Firpo Marberry and the Senators, 11–7.
August 6 - Three American League teams put up ten runs, as the Chicago White Sox defeat the Boston Red Sox 10-0, the New York Yankees defeat the Detroit Tigers 10-4 and the Washington Senators defeat the St. Louis Browns 10-3.
August 30 - After being swept by the St. Louis Browns at Sportsman's Park, the Washington Senators come back and sweep the Chicago White Sox at Comiskey Park. They sweep the second place Philadelphia Athletics on September 1 & 2 to build a 5.5 game lead, and coast the remainder of the way to their second consecutive American League championship.
September 27 - 1925 National League Most Valuable PlayerRogers Hornsby goes three-for-three to raise his batting average to .403. The Cardinals, however, lose 7-6 to the Boston Braves. With the Cards 19 games back of first place, Hornsby sits out the remaining four games on his team's schedule to secure a .400 average for the third time in his career.
Leo Durocher makes his major league debut in the Yankees' 10-0 loss to the Philadelphia Athletics.
Replacing Rogers Hornsby at second base in the St. Louis Cardinals' line-up, Specs Toporcer is the hitting star of the Cardinals' 4-3 victory over the Chicago Cubs with a home run, double and two runs scored. Toporcer goes eight-for-eighteen filling in for Hornsby in the final four games on the Cardinals' schedule.
October 4 - Ty Cobb pitches a 1-2-3 ninth inning in the Detroit Tigers' 11-6 victory over the St. Louis Browns.
October 7 - Walter Johnson's pitching leads the Washington Senators to a 4-1 victory over the Pittsburgh Pirates in game one of the 1925 World Series. Senators shortstop Roger Peckinpaugh commits the first of a record eight errors in the series.
October 10 - The Washington Senators come from behind to take game three of the World Series.
October 11 - Walter Johnson wins his second game of the 1925 World Series, holding the Pirates to six hits, and no runs.
October 12 - The Pirates take game five of the World Series, 6-3. Clyde Barnhart is the hitting star of the game, going two-for-four with two RBIs and a run scored.
October 13 - Eddie Moore leads the fifth inning off with a home run to break a 2-2 tie as the Pirates even the World Series at three games apiece.
October 15 - Walter Johnson again took the mound for Game seven, and carried a 6–4 lead into the bottom of the seventh inning, but errors by 1925 American League Most Valuable Player Roger Peckinpaugh in the seventh and eighth innings lead to four unearned runs, and the Pittsburgh Pirates defeat the Washington Senators, 9-7. The Pirates become the first team in a best-of-seven Series to overcome a 3–1 Series deficit to win the World Championship.
January 1 - Hank Simon, 62, outfielder for the Cleveland Blues, Brooklyn Gladiators and Syracuse Stars of the American Association between the 1887 and 1890 seasons.
January 16 - George Bignell, 66, backup catcher for the 1884 Milwaukee Brewers of the Union Association.
January 24 - Jim Mullin, 41, infielder who played from 1904 through 1905 for the Philadelphia Athletics and Washington Senators of the American League.
January 25 - Cy Bowen, 63, pitcher for the 1896 New York Giants of the National League.
February 15 - Duke Farrell, 58, durable catcher who caught 1565 games from 1888 to 1905 while playing with seven different teams, particularly for the 1903 Boston Americans, the champion team in the first World Series ever played, and also a four-time .300 hitter who led the American Association in home runs and runs batted in 1891.
February 18 - Charlie Dougherty, 63, infielder/outfielder for the 1884 Altoona Mountain City of the Union Association.
February 20 - John Mansell, 66, outfielder for the 1882 Philadelphia Athletics of the American Association.
March 4 - John Montgomery Ward, 65, Hall of Fame pitcher who posted 164-102 record and a 2.10 earned run average in 293 games, including 47 wins for 1879 champion Providence Grays and a perfect game in 1880. He then became a shortstop, batting over .325 three times, to become the fifth player to reach the 2000 hit club. In addition, he organized the first players' union in 1888, and formed the Players League in 1890.
March 21 - Harry Raymond, 63, infielder who played with the Louisville Colonels of the American Association (1888–1891) and for the Pittsburgh Pirates and Washington Senators of the National League (1892).
March 23 - Tom Evers, 72, second baseman for the 1882 Baltimore Orioles of the American Association and the 1884 Washington Nationals of the Union Association.
April 18 - Charles Ebbets, 65, owner of the Brooklyn Dodgers National League franchise since 1897.
April 19 - Suter Sullivan, 52, infielder/outfielder who played from 1898 to 1899 for the Cleveland Spiders and Baltimore Orioles of the National League.
April 23 - Ad Gumbert, 56, pitcher who collected a 123-102 record for the Chicago Cubs, Boston Reds, Pittsburgh Pirates and Philadelphia Phillies from 1888 through 1896.
April 27 - Fred Crane, 84, first baseman for the Elizabeth Resolutes (1873) and the Brooklyn Atlantics (1875) of the National Association of Professional Base Ball Players.
May 9 - Ed Beatin, 58, National League pitcher for the Detroit Wolverines and Cleveland Spiders from 1887 to 1891, and a member of the 1887 champion Wolverines.
May 10 - Tod Brynan, 61, National League pitcher/left fielder for the Chicago White Stockings (1888) and the Boston Beaneaters (1891).
May 31 - Harry Deane, 79, National Association outfielder for the Fort Wayne Kekiongas (1871) and the Baltimore Canaries (1874), who also managed briefly the Fort Wayne team.
June 5 - Sam Trott, 66, National League catcher for the Boston Red Caps, Detroit Wolverines and Baltimore Orioles, who later managed the Washington Statesmen in 1891.
June 26 - Sam Crane, 71, 19th century second baseman in seven seasons for the New York Metropolitans, Cincinnati Outlaw Reds, Detroit Wolverines, St. Louis Maroons, New York Giants and Pittsburgh Alleghenys, who also managed and later went on to a long career as a sportswriter.
July 4 - George Derby, 87, pitcher for the Detroit Wolverines (1881–1882) and Buffalo Bisons (1885) of the National League, who led the circuit for the most strikeouts in 1881.
August 2 - Patrick T. Powers, 63, founder of the minor leagues' governing body and its first president from 1901 to 1909.
August 14 - Asa Stratton, 72, shortstop who played for the 1881 Worcester Ruby Legs.
August 15 - Arthur Soden, 80, owner of the National League's Boston Red Stockings/Beaneaters/Doves/Rustlers/Braves franchise from the 1870s to the 1900s (decade), who became the league's president in 1882.
September 5 - Emil Huhn, 33, first baseman and catcher for the Federal League's Newark Pepper (1915) and the National League's Cincinnati Reds (1916–1917).
September 11 - Pat Duff, 50, pinch-hitter for the 1906 Washington Senators of the American League.
September 21 - Charlie Irwin, 56, third baseman who played from 1893 through 1902 for the Chicago Colts, Cincinnati Reds and Brooklyn Superbas of the National League.
September 22 - Dave Beadle, 61, catcher/outfielder for the 1884 Detroit Wolverines of the National League.
October 7 - Christy Mathewson, 45, Hall of Fame pitcher for the New York Giants, whose 373 victories and a 2.13 earned run average included two no-hitters and thirteen 20-win seasons. Notably, Mathewson reached 30 wins four times and posted an ERA under 2.00 five times, including a National League record of 37 wins in 1908, while leading the circuit in ERA and strikeouts five times each; in wins and shutouts four times, setting league's career records for wins, strikeouts, games and shutout. Other of his highlights includes having pitched three shutouts in a six-day span to lead the Giants to the 1905 World Series title.
October 21 - Marv Goodwin, 34, former pitcher for the Washington Senators, St. Louis Cardinals and Cincinnati Reds between 1916 and 1925, and one of the original spitballers who was grandfathered when that pitch was deemed illegal.
October 19 - John Carney, 58, National League first baseman for the Washington Nationals, Buffalo Bisons and Cleveland Infants from 1889 to 1890.
October 28 - Willy Wilson, 41, pitcher for the 1906 Washington Senators of the American League.