After playing one season with the Newark Eagles in the Negro Leagues, Newcombe signed with the Dodgers. With catcher Roy Campanella, Newcombe played for the first racially integrated baseball team based in the United States in the 20th century, the 1946 Nashua Dodgers of the New England League. He continued to play for Nashua in 1947 before moving up through the minor leagues.
He debuted for Brooklyn on May 20, 1949. He immediately helped the Dodgers to the league pennant as he earned seventeen victories, led the league in shutouts, and pitched 32 consecutive scoreless innings. He was also among the first four black players to be named to the All-Star team, along with teammates Jackie Robinson and Roy Campanella and the Indians’ Larry Doby. Newcombe was named Rookie of the Year by both The Sporting News and the Baseball Writers Association of America. In 1950, he won 19 games, and twenty the following season, also leading the league in strikeouts in 1951. In the memorable playoff game between the Dodgers and the Giants at the end of the 1951 season, Don Newcombe was relieved by Ralph Branca in the bottom of the ninth inning before Branca surrendered the walk-off home run to Bobby Thomson.
After two years of military duty during the Korean War, Newcombe suffered a disappointing season in 1954, going 9-8 with a 4.55 earned run average, but returned to form the next year by finishing second in the NL in both wins and earned run average, with marks of 20-5 and 3.20, as the Dodgers won the first World Series in franchise history. He had an even greater 1956 season, with marks of 27-7, 139 strikeouts, and a 3.06 ERA, five shutouts and 18 complete games, leading the league in winning percentage for the second year in a row. He was named the National League’s MVP, and was awarded the first-ever Cy Young Award, then given to the best pitcher in the combined major leagues.
Following the Dodgers’ move to Los Angeles, Newcombe got off to an 0-6 start in 1958 before being traded to the Reds for four players in midseason. He posted a record of 24-21 with Cincinnati until his contract was sold to Cleveland in mid-1960. He finished with a 2-3 mark in Cleveland before being released to end his major league career. Newcombe acknowledges that alcoholism played a significant role in the decline of his career.
In his 10-year major league career, Newcombe registered a record of 149-90, with 1129 strikeouts and a 3.56 ERA, 136 complete games, and 24 shutouts in 2154 innings pitched. In addition to his pitching abilities, Newcombe was a dangerous hitter as well, having hit seven homers one season. He batted .271 (ninth-best average in history among pitchers), with 15 home runs, 108 runs batted in, 238 hits, 33 doubles, 3 triples, 94 runs scored and 8 stolen bases.