Playing as a half back flanker initially, Mohr later became one of the league's greatest full forwards; he kicked 101 goals in 1936 (the first St Kilda player to kick more than 100 goals in a season) and was the VFL Leading Goalkicker in that year.
Mohr possessed an ability to kick straight from any angle, and was one of the best exponents of the drop kick. He was appointed captain of St Kilda in 1937, and was the club's leading goalkicker in every season from 1929 to 1940. It was announced that at the start of his final season, 1941, he would play in defence. But in May that year, after having only played one game for the season, Mohr announced his retirement, saying that he felt he could not reach form and that it was also time to make way for a younger player.
Bill Mohr was hampered by playing with a comparatively weak St. Kilda combination. In a stronger team he might easily have qualified for a higher place in full forward rankings. An extremely heady player, he was an accurate kick and dependable mark.