January 27 – Fred Saigh buys out the interest of Robert Hannegan and now controls 90 percent of the St. Louis Cardinals stock. Saigh and Hannegan had swung the deal in 1947 with only $60,300 in cash in a $4 million deal. Hannegan came out with $866,000 profit in two years.
January 28 – The New York Giants sign their first black players, Negro Leaguers Monte Irvin (OF) and Ford Smith (P). They are assigned to minor league Jersey City. Irvin will star for the Giants, but Smith never makes the major leagues.
At pregame ceremonies marking the season opener in Yankee Stadium, a granite monument to Babe Ruth is unveiled in center field. Plaques honoring Lou Gehrig and Miller Huggins are also presented. Mrs. Babe Ruth, Mayor William O'Dwyer, and Governor Thomas E. Dewey are at the game.
In Brooklyn, the Dodgers pay tribute to Jack "Shorty" Laurice, the "number one" fan and leader of the Ebbets Field "Sym-phony" band. Laurice died in 1948.
April 28 – A New York fan charges Leo Durocher with assault after the Giants lose 15–2 to Brooklyn. Commissioner Happy Chandler suspends Durocher but he is absolved on May 3. Chandler criticizes teams for lax security that allows fans on the field.
April 30 – Rocky Nelson hits an "inside-the-glove" two-run home run in short center-left field to turn a ninth inning 3–1 Chicago Cubs lead into a 4–3 St. Louis Cardinals victory. Cubs center fielder Andy Pafko's catch is ruled a trap by umpire Al Barlick, as Pafko races in, holding the ball high as runners circle the bases.
May 1 – Elmer Valo becomes the first AL player to hit two bases-loaded triples in a game when he leads the Philadelphia Athletics to a 15–9 win in the first of two games against the Washington Senators. Valo will have a third bases-loaded triple during the season, to tie the AL mark of Shano Collins set in 1918. The A's take game 2, 7–3, called after seven innings.
Before the start of a series with the New York Yankees, the Chicago White Sox abandon their trick left-field fence. The 5-foot chicken wire fence, erected to cut the distance by 20 feet, resulted in 11 home runs in eight games, but opponents hit seven of them. The AL will subsequently rule that fences cannot be moved more than once a season. The Yankees still win today, 7–5, to go 13–3. Tommy Henrich has the only homer, while Johnny Lindell, Yankees left fielder, twice makes catches that would've cleared the wire fence. Allie Reynolds, with help from Joe Page, is the winning pitcher.
At Cleveland, Bob Feller, making his first start since pitching two innings in the season opener and coming up with a sore shoulder, beats the Boston Red Sox 7–3. Cleveland scores six runs in the second inning, including a three-run home run by Ken Keltner off Jack Kramer. On the next pitch, rookie Minnie Miñoso, making his second start, hits his first major-league homer. Ted Williams and Bobby Doerr hit 8th-inning homers for the Red Sox, while Joe Gordon adds a homer in the 5th for Cleveland.
May 6 – Philadelphia Athletics pitcher Bobby Shantz makes a sensational debut, tossing nine hitless innings in relief in a 13-inning 5–4 Athletics win over the Detroit Tigers. Shantz finally gives up two hits and a run in the 13th, but old-timer Wally Moses, now back with the A's, saves him with a two-run home run in the bottom of the 13th.
May 14 – Roy Sievers hits a home run and a double to drive in four runs, leading the St. Louis Browns' 8–3 victory over the Detroit Tigers. Slick-fielding Detroit first baseman Paul Campbell ties a major league record by making two unassisted double plays. While with minor league Montreal in 1941, Campbell started 26 DPs at 1B.
May 22 – Brooklyn Dodgers pitcher Don Newcombe makes his first major league start a dandy, shutting out the Cincinnati Reds 3–0 in the first game of a doubleheader at Crosley Field. It's the first shutout in an NL debut in eleven years and extends Brooklyn's win streak at Cincinnati to 19 games going back to June 1947. Newcombe gives up hits to the first two batters, then allows just three more hits while walking none. He drives in two runs as well. In the second game, Ken Raffensberger then matches Newcombe by firing a one-hitter to beat Brooklyn 2–0, tossing only 83 pitches. The only hit is a leadoff single by Gil Hodges in the eighth inning. Raffensberger pitched two one-hitters against the Dodgers in the 1948 season.
May 24 – Striking out the last six St. Paul batters, Maurice McDermott of minor league Louisville fans a total of 20 for a new league record. McDermott wins 3–1, striking out the side in the 3rd, 5th, 6th, 8th, and 9th innings.
May 27 – The Cleveland Indians start the season so badly, 12–17, that owner Bill Veeck arranges a "Second Opening Day." Behind pitcher Al Benton, Cleveland make it a success, beating the Chicago White Sox 4–0. The Indians do rise to second place, within two 1/2 games of the top, but they will finish third, eight games back.
June 5 – Commissioner Happy Chandler lifts the ban on all players who jumped to the Mexican League, starting in 1946. Only Sal Maglie will make a significant mark after the exile. Lou Klein will be the first jumper to make a major-league box score, successfully pinch-hitting on June 16.
Eddie Waitkus of the Philadelphia Phillies is shot by 19-year-old Ruth Steinhagen at Chicago's Edgewater Beach Hotel. She will later be placed in a mental hospital. Waitkus battles for his life and will come back to play the following season.
June 28 – After missing the first 69 games of the season because of an ailing heel, Joe DiMaggio returns to the New York Yankees lineup with a single and a home run to beat the Boston Red Sox 6–4 in a night game at Fenway Park. DiMaggio will hit four homers in a three-game sweep.
August 6 – Luke Appling appears in his 2,154th game as a shortstop, surpassing the major league mark set by Rabbit Maranville. Appling will finish his career with 2,218 games at SS.
August 8 – Carl Furillo returns to the Brooklyn Dodgers lineup after an injury and hits .431 in the final eight weeks of the season. He will finish at .322, fourth best in the NL.
August 9 – Dom DiMaggio's 34-game hitting streak is on the line against Vic Raschi and the New York Yankees. Hitless in his first four at-bats, Dom hits a sinking line drive in the eighth inning that his brother Joe catches at his shoetops. The Boston Red Sox win 6–3 to move 5½ games behind the Yankees. Dom had started his streak after going hitless against Raschi.
September 3 – In American Association action, Columbus Red Birds pitcher Cot Deal started and completed a twenty-inning game against the Louisville Colonels. In addition to winning the game and giving up one earned run during the 20 innings, Deal collected four hits in eight at-bats.
September 9 – Despite terrorizing the NL with his bat and baserunning during the season, Jackie Robinson is picked off base by Dave Koslo, the fourth time this year New York Giants pitchers have nabbed him.
September 13 – For the second time in his career, Ralph Kiner hits home runs in four consecutive at bats, over two games. Kiner performed the same feat in 1947. The two home runs today are numbers 33 and 34. Kiner's 1949 total will include 25 on the road, 29 at Forbes Field, 14 of them in the bullpen enclosure still known as Greenberg Gardens.
September 15 – Pittsburgh Pirates pitcher Tiny Bonham dies following an appendectomy and stomach surgery, just 18 days after his last pitching performance, an 8–2 victory over the Philadelphia Phillies. Mrs. Bonham will receive the first benefits under the players pension plan, $90 a month for 10 years.
September 20 – Jackie Robinson steals home in a 5–0 Brooklyn Dodgers victory against the Chicago Cubs. It is his fifth steal of home this year and the 13th in his three years in the NL. That is the most in the majors since Ben Chapman stole his 15th and last in 1940, his 11th season.
Despite 71 injuries that kept players out of games, Casey Stengel and his New York Yankees have been in first place all season. But today the Boston Red Sox move into a tie for first place with a 4–1 victory over Allie Reynolds. Ted Williams hits his 43rd home run, and Mel Parnell wins his 25th game of the season. Parnell is 16-3 at Fenway Park this year. Joe DiMaggio listens to the game from a hospital, bedridden with pneumonia. The Yankees return to New York and are greeted at Grand Central Station by a huge crowd of fans, including Mrs. Babe Ruth, who predicts, "Whoever wins tomorrow should go all the way."
Called up from Triple-A Toronto in mid-September, Ed Sanicki of the Phillies gets his third hit of the season. All three are home runs. On September 14, Sanicki had homered with two men on his first big-league at bat, against Rip Sewell of the Pittsburgh Pirates.
Coming into the last weekend of the season, the Boston Red Sox are one game ahead of the New York Yankees, with the only games left for those teams being two against each other, thus there can be no playoff for the American League pennant. The Red Sox need to win only one of those games, but the Yankees win both to take the pennant. The Yankees will go on to win 14 pennants in the 16-year stretch from 1949 through 1964.