Hein signed with the New York Giants in 1931, which would be the only team he played for over his fifteen-year career.  Hein played at Center and Linebacker, and he was a massive cog in the Giants teams that won the 1934 and 1938 NFL Championship, and appeared in five other Championship Games.

Hein was such a dominant player that he was a four-time Pro Bowl, five-time First Team All-Pro, and he was named to the 1930s All-Decade Team, as well as the 75^thand 100^thAnniversary Team. Hein entered the Pro Football Hall of Fame in 1963, which would be the same year that New York retired his number 7.  He was also part of the first Giants Ring of Honor class in 2010.