Eisenstat debuted for his hometown Brooklyn Dodgers as a 19-year-old rookie in 1935. He pitched for three teams over eight big-league seasons, mostly as a reliever, but occasionally as a spot starter. On Oct. 2, 1938, when Bob Feller set a live-ball era single-game strikeout record by fanning 18 batters, his Indians still lost the game because Eisenstat earned a complete-game win for Hank Greenberg and the Tigers. Earlier in the season, he pitched nine innings of shutout ball and was the winning pitcher in both ends of a doubleheader against the Athletics while Greenberg hit three home runs, causing Mickey Cochrane to warn the two of them to stay in their rooms that night because “the Jews in Detroit are going crazy.” Eisenstat was traded to Cleveland the following season for future Hall of Famer Earl Averill. In 1942, he enlisted in the Air Force, ending his playing career at the age of 26. After the Second World War, Eisenstat owned a hardware store in Shaker Heights, Ohio.
Harry won 20 games in 1936 — 19 with Allentown of the New York-Penn League and one with the Dodgers.