The New York Metropolitans of the American Association, run by John Day, release Tim Keefe and Dude Esterbrook in order for them to be acquired by the National League New York Giants, also run by Day.
April 29 – After being shut out for the 2nd straight game, players on the Cincinnati Red Stockings are fined $25 each by their manager O. P. Caylor.
May 7 – The St. Louis Browns take over 1st place in the American Association with a 13–1 win over the Philadelphia Athletics and will remain there for the rest of the season.
May 27 – John Montgomery Ward of the New York Giants graduates from the Columbia Law School.
June 2 – The Baltimore Orioles defeat the St. Louis Browns 7–1 to break the Browns 17-game winning streak.
June 7 – The American Association removes all restrictions on overhand pitching.
June 12 – Dave Orr, first baseman for the American Association New York Metropolitans, hits for the cycle. New York defeats the St. Louis Browns, 17–8.
June 13 – Detroit Wolverines outfielder George Wood hits for the cycle in a 17–9 loss to the Chicago White Stockings.
June 16 – Henry Larkin of the American Association Philadelphia Athletics hits for the cycle in a 14–1 win over the Pittsburgh Alleghenys.
June 17 – "Phenomenal" Smith loses his first start as a Brooklyn Gray by a score of 18–5 after his teammates commit 14 errors behind him, including 7 by shortstop Germany Smith. "Phenomenal"'s boast of being so good that he could win by himself doesn't sit well with the other Brooklyn players, who are fined $500 for their intentional poor play. In the interests of team chemistry, Smith is immediately released.
June 25 – 10 different players collect at least 2 hits each for the Brooklyn Grays in their 21–14 win over the Philadelphia Athletics. George Strief of Philadelphia sets a major league record by hitting 4 triples in the game.
July 1 – Tom Burns of the Chicago White Stockings hits a home run that is estimated at 500 feet in a Chicago win.
July 2 – Sam Thompson makes his major league debut for the Detroit Wolverines.
July 3 – Jim McCormick of the Providence Grays wins his 200th career game for his first victory of the season. 6 days later he will be sold to the Chicago White Stockings where he will win 20 games.
July 4 – Owen Keenan of the Youngstown, Ohio club beats New Castle in both games of a double-header, pitching one game right-handed and the other game left-handed.
July 11 – After winning 175 games while pitching over 2,300 innings for the Chicago White Stockings since 1880, pitcher Larry Corcoran is released after straining his arm muscles so badly that he is unable to throw. Corcoran will only pitch 54 more innings and win 2 more games for the remainder of his career.
July 12 – The Buffalo Bisons sell Pud Galvin to the Pittsburgh Alleghenys for $5,000.
July 27 – John Clarkson, in the midst of a 53 win season, pitches a no-hitter for the Chicago White Stockings.
July 29 – Henry Larkin ties the record by hitting 4 doubles in a game.
August 16 – Louis Henke dies of a ruptured liver, sustained in an on-field collision in a Southern League game the previous day.
August 18 – Jack Farrell of the Providence Grays is suspended without pay for shouting obscenities at fans in Providence.
August 26 – Roger Connor of the New York Giants starts a first-inning triple play. 12 days later, Connor would be involved in another first-inning triple play.
August 27 – Paul Hines is released by the Providence Grays after they accuse him of intentionally playing poorly.
August 29 – Charlie Ferguson of the Philadelphia Quakers pitches a no-hitter in a 1–0 win over the Providence Grays.
August 29 – The St. Louis Browns win the American Association pennant with a 16–9 win over the Louisville Colonels.
September 11 – The Providence Grays suspend Charles Radbourn and Jerry Denny after a 9–1 loss.
September 17 – The Detroit Wolverines purchase controlling ownership in the Buffalo Bisons in a move that will be overturned by the National League.
September 19 – With former Buffalo players Dan Brouthers, Hardy Richardson, Jack Rowe and Deacon White in uniform for the Detroit Wolverines, the National League orders their game against the New York Giants forfeited if they play. Detroit sits the 4 new players and loses to the Giants 6–5. The 4 return to Buffalo to finish the season.
September 28 – Detroit Wolverines first baseman Mox McQuery hits for the cycle against the Providence Grays. Detroit wins, 14–2.
September 30 – The Chicago White Stockings clinch the National League pennant with a 2–1 win over the New York Giants.
October 1 – The first all black professional team is formed by Frank P. Thompson. Originally known as the Athletics, they will soon change their name to the Cuban Giants.
October 3 – Playing in an exhibition game against Newark of the Eastern League, the American Association Baltimore Orioles are no-hit by the former (and future) big-leaguer, John "Phenomenal" Smith.
October 7 – Fred Shaw of the Providence Grays throws a 5 inning no-hitter before 12 fans in Buffalo in the first game of a double-header against the Bisons. Shaw beats them again in another 5-inning game in the nightcap.
October 10 – The Providence Grays sweep the Buffalo Bisons in a double-header in the Bison's last day in the major leagues. Buffalo finishes the season with a 17-game winless streak, only managing 1 tie in the season's last 3 weeks.
October 10 – Joe Gerhardt, second baseman of the New York Giants finishes the season with a .155 batting average while shortstop Charlie Bastian of the Philadelphia Quakers ends the year with a .167 average. Both players set still-standing records for the lowest batting average in a season (with a minimum of 350 at-bats) for their respective positions.
October 17 – The National League sets a minimum player salary of $1,000 and a maximum of $2,000 for the 1886 season.
October 22 John Montgomery Ward, along with several teammates, forms the Brotherhood of Professional Base-ball Players, the first union in professional sports history. The Brotherhood would ultimately result in the Players' League in 1890.
October 24 – The final game of the 1885 World Series is played. The St. Louis Browns defeat the Chicago White Stockings 13–4 to tie the series at 3 wins each, with game 1 having ended in a tie.
December 4 – The New York Metropolitans are sold to Canadien-born millionaire Erastus Wiman for $25,000.
December 24 – The St. Louis Browns sell the reserve rights of Sam Barkley to fellow American Association member Baltimore Orioles for $1,000.