In 2011, Goldschmidt played for the Mobile Bay Bears of the Class AA Southern League. He had a .306 batting average, 30 home runs, and 94 RBIs in 103 games played through the end of July, leading all minor leaguers in home runs and RBIs, while his 82 walks was third-best. After the season, Goldschmidt was again named the Diamondbacks' player of the year, a Baseball America first-team Minor League All-Star, Class AA all-star first baseman, Southern League all-star first baseman, and the Southern League's Most Valuable Player.
The Diamondbacks promoted Goldschmidt to the MLB on August 1, 2011. The Diamondbacks intended to platoon Goldschmidt with Xavier Nady. Goldschmidt recorded a base hit in his first MLB at-bat on August 1, and hit his first MLB home run the next day off San Francisco Giants pitcher Tim Lincecum. After Nady broke his wrist in mid-August, the Diamondbacks signed Lyle Overbay to replace him. Goldschmidt has credited Overbay for his mentorship. Goldschmidt struck out 20 times in his first 44 MLB at bats. In his rookie season, Goldschmidt batted .250 with eight home runs and 26 RBIs in 48 games.
The Diamondbacks made the postseason, and played against the Milwaukee Brewers in the 2011 National League Division Series (NLDS). In Game 3, Goldschmidt hit a grand slam to extend the team's lead in its first victory of the series. His home run was the third grand slam by a rookie in MLB postseason history. The Diamondbacks lost the series in five games, and Goldschmidt batted .438 with six RBIs and an OBP of .526.