Cleveland optioned Sundra to Minneapolis and Newark in 1935, and the Yankees obtained him in a three-pitcher deal in December, along with Monte Pearson, in exchange for Johnny Allen.

His career in the American League ran from 1936 to early in 1946, with time out for 1944–1945 United States Army service during World War II.

The Bears won the IL championship with a 109–43 mark, and Sundra went 15–4, ranking eighth in the league in ERA (3.09), and was selected for the All-Star Game.

He appeared in Game Four of the 1939 World Series, pitching 2.2 innings of relief, allowing 4 hits, 3 runs, all unearned, 1 walk and striking out 2.

But after his third start on May 2 he entered the Army, thus missing the 1944 World Series, the only fall classic in which the Browns would ever appear during their 52-year history in the American League.