The Mets signed right-handed pitcher Jim Bethke as an amateur free agent prior to the 1964. After spending the 64 season in the minors, Bethke made his Major League debut as an 18-year-old rookie on April 12, 1965. He pitched a scoreless 9th inning in the Mets 6-1 loss to the Los Angeles Dodgers. Three days later he earned his first win against the Houston Astros. He pitched the final 2/3 of an inning before the Mets won the game on a Bobby Klaus walk-off home run.
In his only season in the Majors Bethke appeared in 25 games, all out of the bullpen, and posted a 2-0 record with a 4.28 ERA. He pitched in the Mets minor league system through 1970
While with the Mets Bethke wore the following numbers 41,28 and 36.