In 1949, the New York Giants paid $5,000 for Irvin's contract. He was one of the first black players to be signed, as
Jackie Robinson had only broken the MLB
color line in 1947. Assigned to Jersey City of the
International League, Irvin batted .373. He debuted with the Giants on July 8, 1949, as a
pinch hitter. Back with Jersey City in 1950, he was called up after hitting .510 with ten home runs in 18 games. Irvin batted .299 for the Giants that season, playing
first base and the outfield. In 1951, Irvin sparked the Giants' miraculous comeback to overtake the Dodgers in the pennant race, batting .312 with 24 homers and a league-best 121
runs batted in (RBI), en route to the
World Series (he went 11–24 for .458). In the third game of the playoff between the Giants and Dodgers, Irvin popped out in the bottom of the ninth inning before
Bobby Thomson hit the
Shot Heard 'Round the World. That year Irvin teamed with
Hank Thompson and
Willie Mays to form the first all-black outfield in the majors. Later, he finished third in the NL's MVP voting. During that season, Giants manager
Leo Durocher asked Irvin to serve as a mentor for Mays, who had been called up to the team in May. Mays later said, "In my time, when I was coming up, you had to have some kind of guidance. And Monte was like my brother ... I couldn't go anywhere without him, especially on the road ... It was just a treat to be around him. I didn't understand life in New York until I met Monte. He knew everything about what was going on and he protected me dearly." Irvin later replied, "I did that for two years and in the third year he started showing me around." However, Irvin returned in time to be named to his only
Major League Baseball All-Star Game in 1952. He appeared in only 46 games that season, hitting .310 with four home runs and 21 RBI. The Giants went on to win the Series in four games, with Irvin collecting two hits in nine at bats. In 1955, Irvin had been sent down to the minor leagues, where he hit 14 home runs in 75 games for the
Minneapolis Millers. The
Chicago Cubs signed him before the 1956 season. The team said that he would compete with
Hank Sauer for a starting position in left field. Irvin appeared in 111 games for the Cubs that year, hitting .271 with 15 home runs. A back injury led to Irvin's retirement as a player in 1957. He sustained the injury during spring training that year and only appeared in four minor league games for the
Los Angeles Angels of the
Pacific Coast League. In his major league career, Irvin batted .293, with 99 home runs, 443 RBI, 366
runs scored, 731
hits, 97
doubles, 31
triples, and 28
stolen bases, with 351
walks for a .383
on-base percentage, and 1187 total bases for a .475
slugging average in 764 games played. Defensively, Irvin recorded a .981
fielding percentage. ==Later life==