Simensen signed with the Los Angeles Rams after going undrafted in the 1951 NFL draft.[3] He played in all 12 games, starting 11 at tackle, for the Rams during his rookie year in 1951.[4] He also started for the Rams in the 1951 NFL Championship Game, a 24–17 victory over the Cleveland Browns.[5] He appeared in 12 games, starting nine, during the 1952 season.[4] He also started one playoff game that year.[4] Simensen became a free agent after the 1952 season.[3]