Cully Dahlstrom played high school hockey at Minneapolis South and then went on to play for the Minneapolis Millers in the American Hockey Association.

The American Hockey Association was a strong minor professional league of that time and sent many promising players into the National Hockey League. It was there that he caught the eye of Major Fed McLaughlin of the Chicago Blackhawks who was always on the lookout for promising American talent. Dahlstrom didn't let McLaughlin down as he won the Calder Trophy as the National Hockey Leagues' rookie of the year 1937-38. In the semi-final playoffs against the New York American's he scored the winning goal in 1-0 overtime victory in the second game. In the finals against Toronto he scored the key first goal in the 4-1 victory which brought the Stanley Cup to the Windy City.

In the 1940-41 Stanley Cup playoffs, Dahlstrom once again had a strong series against the Montreal Canadiens. He scored once in a 4-3 loss and then won the series for the Hawks with two goals in the final 3-2 victory. Chicago was subsequently eliminated by Detroit 2 games to 0. Dahlstrom retired after the 1944-45 season. Appearing in 368 regular and playoff games, he scored 94 and 126 assists. Dahlstrom's most outstanding single season was 1943-44 when he scored 20 goals and 22 assists in the then full 50 game schedule.