At age 22, Bregman started his 2017 baseball season as the youngest member of Team USA in the World Baseball Classic (WBC), which won its first gold medal in the WBC by defeating Puerto Rico 8–0 in the final.
 He had been invited as well to play for Team Israel which finished sixth at the 2017 World Baseball Classic, as WBC rules allow all Jewish ballplayers to play for the team, and he later said that in retrospect "I probably should've" played for Team Israel "because I got [just] four at-bats" playing as a backup for Team USA.

He was the youngest Opening Day third baseman in team history, at 23 years and 4 days old.
During the May 14, 2017, game versus New York at Yankee Stadium, Bregman hit his first major league grand slam off Masahiro Tanaka in a 10–7 Astros win.
On August 10, Bregman tied the Astros' record for extra-base hits in consecutive games at 10 games, first accomplished by outfielder Richard Hidalgo.

For the 2017 season, he batted .284/.352/.475 with 39 doubles and five triples (the latter two both ninth in the AL), 19 home runs, 88 runs, 71 RBIs, and 17 stolen bases (tied for the lead among all major league third basemen).
His .331 batting average against left-handers was 9th in the AL.
 Bregman played third base primarily (132 games), and led AL third basemen in fielding percentage (.970; the 4th-highest fielding percentage by a third baseman in team history), while also playing 30 games at shortstop.
 Houston won the AL West division with a 101–61 record, thus advancing Bregman to his first career major league playoff.

Bregman was a major force for the Astros throughout the 2017 postseason.
His home run off of Chris Sale, his second off of Sale in the series, in the 8th inning of Game 4 of the ALDS tied the game 3-3 and jump-started the Astros' rally that led them to a 5-4 win over the Red Sox and propelled them to their first appearance in a Championship Series since 2005.
Bregman also showcased his defensive skills throughout the postseason, but especially during the ALCS against the Yankees.
In Game 7, with the Astros up 1-0 with Yankees on first and third in the top of the 5th, Bregman threw out Greg Bird at home on a chopper to third off of the bat of Todd Frazier to help preserve the lead.
It helped lead the Astros to a 4-0 victory in the pennant-clinching game.

Bregman would once again throw out a runner at home from third base in Game 4 of the World Series against the Los Angeles Dodgers, when he gunned down Austin Barnes at the plate in the top of the 6th inning to preserve a 0-0 tie.
Bregman also homered off of Kenley Jansen in the bottom of the 9th, but the Astros ultimately fell 6-2.
His biggest contribution came during Game 5 when, after a back-and-forth game in which the Astros came back from two separate 3-run deficits, Bregman hit a walk-off single in the bottom of the 10th inning off Jansen to give the Astros a 13-12 victory and a 3–2 series lead.
It was Bregman's first career walk-off hit.
He became the second player to drive in a run in each of his first five World Series games, joining Amos Otis.
 The series lasted seven games, and the Astros won the World Series for the first time ever.

 Bregman finished his first postseason with 4 home runs and 10 RBIs.
At age 22, Bregman started his 2017 baseball season as the youngest member of Team USA in the World Baseball Classic (WBC), which won its first gold medal in the WBC by defeating Puerto Rico 8–0 in the final.  He had been invited as well to play for Team Israel which finished sixth at the 2017 World Baseball Classic, as WBC rules allow all Jewish ballplayers to play for the team, and he later said that in retrospect "I probably should've" played for Team Israel "because I got [just] four at-bats" playing as a backup for Team USA.
He was the youngest Opening Day third baseman in team history, at 23 years and 4 days old. During the May 14, 2017, game versus New York at Yankee Stadium, Bregman hit his first major league grand slam off Masahiro Tanaka in a 10–7 Astros win. On August 10, Bregman tied the Astros' record for extra-base hits in consecutive games at 10 games, first accomplished by outfielder Richard Hidalgo.
For the 2017 season, he batted .284/.352/.475 with 39 doubles and five triples (the latter two both ninth in the AL), 19 home runs, 88 runs, 71 RBIs, and 17 stolen bases (tied for the lead among all major league third basemen). His .331 batting average against left-handers was 9th in the AL.  Bregman played third base primarily (132 games), and led AL third basemen in fielding percentage (.970; the 4th-highest fielding percentage by a third baseman in team history), while also playing 30 games at shortstop.  Houston won the AL West division with a 101–61 record, thus advancing Bregman to his first career major league playoff.
Bregman was a major force for the Astros throughout the 2017 postseason. His home run off of Chris Sale, his second off of Sale in the series, in the 8th inning of Game 4 of the ALDS tied the game 3-3 and jump-started the Astros' rally that led them to a 5-4 win over the Red Sox and propelled them to their first appearance in a Championship Series since 2005. Bregman also showcased his defensive skills throughout the postseason, but especially during the ALCS against the Yankees. In Game 7, with the Astros up 1-0 with Yankees on first and third in the top of the 5th, Bregman threw out Greg Bird at home on a chopper to third off of the bat of Todd Frazier to help preserve the lead. It helped lead the Astros to a 4-0 victory in the pennant-clinching game.
Bregman would once again throw out a runner at home from third base in Game 4 of the World Series against the Los Angeles Dodgers, when he gunned down Austin Barnes at the plate in the top of the 6th inning to preserve a 0-0 tie. Bregman also homered off of Kenley Jansen in the bottom of the 9th, but the Astros ultimately fell 6-2. His biggest contribution came during Game 5 when, after a back-and-forth game in which the Astros came back from two separate 3-run deficits, Bregman hit a walk-off single in the bottom of the 10th inning off Jansen to give the Astros a 13-12 victory and a 3–2 series lead. It was Bregman's first career walk-off hit. He became the second player to drive in a run in each of his first five World Series games, joining Amos Otis.  The series lasted seven games, and the Astros won the World Series for the first time ever.
 Bregman finished his first postseason with 4 home runs and 10 RBIs.
Alex Bregman