The 1938 major league baseball season began on April 18, 1938. The regular season ended on October 2, with the Chicago Cubs and New York Yankees as the regular season champions of the National League and American League, respectively. The postseason began with Game 1 of the 35th World Series on October 5 and ended with Game 4 on October 9. The Yankees swept the Cubs in four games.
The 1938 schedule consisted of 154 games for all teams in the American League and National League, each of which had eight teams. Each team was scheduled to play 22 games against the other seven teams of their respective league. This continued the format put in place since the 1904 season (except for 1919) and would be used until 1961 in the American League and 1962 in the National League.
American League Opening Day took place on April 18 with four teams playing, while National League Opening Day took place the following day, featuring all eight teams. This was the first season since 1932 that both leagues opened on different days. The final day of the regular season was on October 2 and featured all sixteen teams, continuing the trend since the previous season. The World Series took place between October 5 and October 9.