April 1 – Starting off with a bang, Japanese star Sadaharu Oh hits a grand slam home run on opening day. It is his 757th home run.
April 13 – The New York Yankees defeat the Chicago White Sox 4–2 in their home opener on Reggie Candy Bar Day. Reggie Jackson slugs a 3-run home run in the first inning, and the field is showered with candy bars which were given out free to the fans at the game.
April 20 – With two out in the top of the fourth inning, the Atlanta Braves' Jeff Burroughs hits a ground ball up the middle that San Diego Padres rookie shortstopOzzie Smith dives behind second after. As he was in the air, the ball hits the base, and caromes behind Smith. As he is diving in the opposite direction, Smith reaches out with his bare hand and catches the ball. He bounces up, and throws Burroughs out at first. The Padres win the game 2–0.
May 14 – With the Chicago Cubs losing 7–5 to the Los Angeles Dodgers, Dave Kingman hits a two run home run with two outs in the ninth inning to send the game into extra innings. Kingman, who had also homered in the sixth, hits his third home run of the day in the fifteenth inning to give the Cubs a 10–7 victory over the Dodgers at Dodger Stadium, and end his day with eight RBIs. Following the game, Paul Olden, a reporter for radio station KLAC in Los Angeles asks Dodgers manager Tommy Lasorda, "What's your opinion of Kingman's performance?" during his post-game interview. Lasorda goes off in a now famous obscenity laced tirade.
June 16 – In his 12th major league season speckled with near-misses, Cincinnati's Tom Seaver finally hurls a no-hitter. The Cardinals are the 4–0 victims as Seaver strikes out 3 batters.
June 17 – The Yankees' Ron Guidry strikes out 18 batters — 15 in 6 innings — in a 4–0 shutout of the California Angels, setting an American League record for left-handers. The victory raises the New York Yankee southpaw's record to 11–0.
June 30 – In the first game of a 10–9, 10–5 doubleheader loss to the Atlanta Braves, the San Francisco Giants' Willie McCovey hits his 500th career home run, off Braves pitcher Jamie Easterly. McCovey becomes the 12th member of the 500th home run club. Giant Mike Ivie adds his 2nd pinch grand slam of the year in the opener. Giant Jack Clark has 3 runs in the 2 games.
July 13 – Jerry Koosman and Tom Seaver lock up for the second time since Seaver's trade to the Cincinnati Reds. Koosman and the Mets beat Seaver and the Reds, 4–2. Only one of the three runs Seaver gives up is earned.
July 17 – The Kansas City Royals defeated the New York Yankees 9-7 in 11 innings, but the game is remembered for Reggie Jackson ignoring signs from third-base coach Dick Howser with the score tied 5-5 in the bottom of the 10th. With Thurman Munson on first, manager Billy Martin wanted Jackson to sacrifice bunt. Jackson made a half-hearted attempt with the first pitch, and Martin removed the bunt sign. Jackson, however, defied Martin and still attempted a bunt, but ended up striking out. Jackson was suspended by Martin for five games.
July 21 – As Reggie Jackson was returning from suspension, Billy Martin said in a post-game interview about Jackson and Yankee owner George Steinbrenner, "One's a born liar (referring to Jackson), and the other's convicted (referring to Steinbrenner, about an incident from the past when Steinbrenner was accused of making illegal presidential campaign contributions)." Martin later was shown on live television tearfully announcing his resignation from the Yankees, although some sources believed Steinbrenner actually fired him. Bob Lemon was named Yankee manager for the remainder of the season.
July 26 – Johnny Bench hits his 300th career home run.
August 1 – The Atlanta Braves trounce the Cincinnati Reds, 16–4, and stop Pete Rose's hitting streak at 44 games. Larry McWilliams and Gene Garber are the Atlanta pitchers. Rose goes 0-for-4, including striking out in the 9th inning to end the game. Rose's streak is the second-longest in major league history. He goes 70-for-182 during the skein (a batting average of .385).
August 5 – At Old-timers Day at Yankee Stadium, recently fired Billy Martin is announced as the New York Yankees' manager for the 1980 season.
September 5 – The Montreal Expos beat the Chicago Cubs 10–8 in a 9-inning game that sees a Major-League record 45 players participate.
September 7 – The "Boston Massacre" begins. The Boston Red Sox enter today's opening game of a four game series in Boston with a four game lead over the New York Yankees; a lead which had been fourteen games just weeks earlier. The Yankees defeat the Red Sox 15–3, and go on to sweep the series, erasing the Red Sox lead in the American League East Division.
September 14 – 39-year-old Atlanta Braves pitcher Jim Bouton earns his 62nd and final big league victory (his first since 1970), a 4–1 win over the San Francisco Giants. Bouton is best known as the author of the baseball diary Ball Four.
September 20 – The Yankees' Ron Guidry suffers his third and final loss in a stellar 25-3, Cy Young Award-winning season. The Yankees are defeated by the Toronto Blue Jays with left-hander Mike Willis the winning pitcher. All three of Guidry's losses in 1978 were to left-handers named "Mike": Mike Caldwell, Mike Flanagan, and Willis.
Led by home runs from Rick Burleson and Jim Rice, and Luis Tiant's two-hit pitching, the Boston Red Sox shut out the Toronto Blue Jays 5–0 at Fenway Park, closing out the regular season with an eight-game winning streak. They will have to play a one-game playoff at Fenway the very next day against the New York Yankees, whom they had led by as many as 14 games in July, as the Cleveland Indians and Rick Waits defeat the Yankees 9–2 at Yankee Stadium. News of the Indians' victory is announced on Fenway Park's video screen with the words "THANK YOU, RICK WAITS – GAME TOMORROW."
November 28 – The Cincinnati Reds dismiss their nine-year manager, Sparky Anderson, who had led the team to five NL Division titles, four NL Championship pennants, two World Championships (1975–76), and averaged 96 wins per season. Anderson will become the manager of the Detroit Tigers in 1979, replacing Les Moss.
January 7 – George H. Burns, 84, first baseman for five AL teams who batted .307 lifetime and won 1926 MVP award with the Cleveland Indians
January 13 – Bill Clowers, 79, pitcher for the Boston Red Sox in the 1920s
January 13 – Merwin Jacobson, 83, backup outfielder for the New York Giants, Chicago Cubs and Brooklyn Robins between 1915 and 1927
January 13 – Joe McCarthy, 90, Hall of Fame manager who led the New York Yankees to eight pennants and record seven World Series titles; also won 1929 NL pennant with Chicago Cubs, and was first manager to capture titles in both leagues; 2125 career wins ranked 4th in major league history, and winning percentages of .615 (regular season) and .698 (postseason) were both records
January 27 – Monte Pearson, 69, All-Star pitcher who won 100 games, mainly with the Indians and Yankees
February 3 – Mike Herrera, 80, second baseman for the Boston Red Sox from 1925–26, and one of the first men to play in both the major leagues and the negro leagues
February 8 – Josephine Kabick, 55, female pitcher who played from 1944 through 1947 in the AAGPBL
February 23 – Vic Harris, 72, outfielder and manager in the Negro Leagues who guided the Homestead Grays to seven Negro National League pennants, including five in a row from 1937 to 1941; played in six East-West All-Star games between 1933 and 1947
March 12 – Gene Moore, 68, All-Star right fielder known for his accurate arm
March 21 – Fritz Coumbe, 88, a pitcher for the Boston Red Sox, Cleveland Naps & Indians, and Cincinnati Reds between 1914 and 1921
March 30 – Billy Cox, 58, third baseman, mainly with the Brooklyn Dodgers, known for spectacular defense
April 8 – Ford Frick, 83, Hall of Fame executive who served as commissioner from 1951 to 1965 and NL president from 1935 to 1951; served as ghostwriter for Babe Ruth while a sportswriter, and in 1961 ruled that home run records of Ruth and Roger Maris would be recorded separately based on season length
April 14 – Joe Gordon, 63, 9-time All-Star second baseman in 11 seasons for the New York Yankees and Cleveland Indians who won the 1942 MVP award; set AL record of 246 home runs at his position, later a manager and scout
April 15 – Nick Cullop, 78, outfielder for the New York Yankees, Washington Senators, Cleveland Indians, Brooklyn Robins and Cincinnati Reds, and also a longtime player/manager at minor league level
April 20 – Jack Graney, 91, Canadian left fielder and leadoff hitter for the Cleveland Indians who led AL in walks twice and doubles once; was first batter ever to face Babe Ruth, and later became broadcaster
May 29 – Carl Reynolds, 75, outfielder for five teams who batted .302 lifetime
August 5 – Jesse Haines, 85, Hall of Fame pitcher who won 210 games, including a no-hitter, for the St. Louis Cardinals; had three 20-win seasons, and won twice in 1926 World Series
August 15 – Ed Chaplin, 84, catcher for the Boston Red Sox between 1920 and 1922
August 18 – George Harper, 86, outfielder for six teams who batted .300 three times
September 16 – Bill Foster, 74, star pitcher in the Negro Leagues where he was a dominant left-hander; later coached at Alcorn State University for two decades
September 23 – Lyman Bostock, 27, outfielder for the Minnesota Twins and California Angels who twice batted .300
October 8 – Jim Gilliam, 49, All-Star infielder for the Brooklyn and Los Angeles Dodgers, previously in the Negro Leagues, who was the 1953 Rookie of the Year; led NL in triples and walks once each
October 16 – Eddie Stumpf, 84, Minor league player, manager, coach, scout and executive in a career than spanned more than four decades
October 27 – Rube Walberg, 82, pitcher who won 155 games, primarily with the Philadelphia Athletics
November 5 – Tommy O'Brien, 59, backup outfielder for the Pirates, Red Sox and Senators in the late 1940s
November 20 – Warren Brown, 84, Chicago sportswriter
December 9 – Dick Siebert, 66, All-Star first baseman for the Philadelphia Athletics who twice batted .300; coach at the University of Minnesota for 31 years, winning three College World Series titles
December 12 – Nick Dumovich, 76, pitcher for the 1923 Chicago Cubs
December 20 – Willard Mullin, 76, cartoonist whose caricature of the "Brooklyn Bum" personified the Dodgers franchise
December 24 – George McQuinn, 68, 7-time All-Star first baseman for the Browns and Yankees who had 34-game hitting streak in 1938
December 24 – Bill Rodgers, 91, second baseman who played between 1915 and 1916 for the Cleveland Indians, Boston Red Sox and Cincinnati Reds