The Mets acquired right-handed pitcher Gary Kroll from the Philadelphia Phillies along with Wayne Graham on August 7, 1964 in exchange for Frank Thomas. He made his Met debut on August 22 against the Chicago Cubs. As the starter he lasted six innings and allowed three runs by suffered the loss as the Mets lost 3-2. He appeared in 8 games, two as a starter, and finished with a 0-1 record and 4.15 ERA.
He returned in 1965 and split time between the starting rotation and bullpen. He appeared in 32 games and posted a 6-6 record with a 4.45. He started 11 games and went 2-5 with a 6.22 ERA. He appeared in 21 games out of the bullpen and posted a 4-1 record with a 2.43 ERA. He earned his first career victory in his first appearance of 1965 on April 18. He allowed 4 hits and 1 run over 7 innings as the Mets won 7-1.
Following the season, the Mets traded Kroll to the Houston Astros. In 40 appearances for the Mets he went 6-7 with a 4.39 ERA.
While with the Mets Kroll wore number 25.
Gary Kroll also played for the following teams:
Philadelphia Phillies – 1964
Houston Astros – 1966
Cleveland Indians – 1969