Two days after being released by Pittsburgh, Klinger was signed by Boston, where he served primarily as a relief pitcher. During the 1946 regular season, he made 28 appearances with just 1 start – a no decision in his first appearance – and had a league-leading 9 saves, with a 3–2 record and a 2.37 ERA. That year, the Red Sox ran away with the American League crown by twelve games over the Detroit Tigers with a 104–50 record, and were heavy favorites in the World Series against the St. Louis Cardinals, however the series went the full seven games.