His first season with the club, 1923-24 would be by the record books a slow season for Joe as he had 1 goal and 1 assist in 6 games. He improved these numbers in his second season when he went to the Toronto St. Mary's, also in the OHA, and notched 7 goals and 3 assists in 8 games. In 1925-26 Joe started to find himself and led the OHA with 15 goals, added 2 assists, which gave him the lead in the league for most points with 17.

The Toronto Marlboros of the OHA Sr. loop was the next stop for Primeau in 1926-27 where he popped 11 goals and 3 assists for 14 points in 11 games. At the same time in New York, Conn Smythe was in the process of putting together the New York Rangers and he remembered Primeau, recommending that the Rangers sign him. The Ranger's organization was reluctant to sign a player of Primeau's size and passed on the recommendation.

Shortly thereafter, Smythe was relieved of his duties with the Rangers and promptly proceeded to Toronto and purchased the Toronto St. Patricks and renamed them the Toronto Maple Leafs. One of his first moves was to sign Joe Primeau and did so on July 17, 1928. Joe made a few brief appearances with the Leafs in 1927-28 and 1928-29 but in 8 games he managed only a single assist.

The 1929-30 season was Joe's first complete NHL season with the Leafs and it proved to be a good one, and it was the first season that Primeau's play making ability would shine through. Never again would his goal total exceed his assist total. Sometime in 1930, Smythe teamed up Primeau with Harvey "Busher" Jackson and Charlie "the Big Bomber" Conacher to form the "Kid Line." They got their name because all 3 were inexperienced youngsters, but despite their youth, they became the most famous Toronto line of all time.

Primeau led the league in assists in 1930-31 with 32, and later repeated the feat in 1931-32 and 1933-34 with 37 and 32 respectively. The pinnacle of Joe's career came in 1931-32 when he tallied 50 points on 13 goals and 37 assists, finishing a mere 3 points behind his team mate Jackson for the league scoring title. That same season, the Leafs took the Stanley Cup with Joe again leading the league in assists during the playoffs with 6 in 7 games. Joe again finished second in the scoring race in 1933-34 with 46 points, this time 6 points behind his other line mate, Charlie Conacher who finished the season with 52 points.

The following season Joe broke his thumb in a pre-season exhibition game, causing him to miss 11 games, and that spelled the end of the "Kid Line." Joe retired at the end of the next season to devote more time to his construction business, finishing up his career with 66 goals, 177 assists for 243 points in 310 regular season games.

By 1938-39 Joe was back in hockey as coach of the Toronto Marlboro's Senior team, and also coached the Toronto RCAF Hurricanes in 1942-43. Primeau returned to the St. Michael's organization and in 1944-45 and in 1945-46 he coached them to Memorial Cup victories. After joining the Marlie's Senior team, he guided them to the Allan Cup Championship in 1949-50. He was then hired by the Toronto Maple Leafs and took them to a Stanley Cup victory in 1950-51. This "Triple Crown" of the Memorial, Allan and Stanley Cup Championships made Joe the first and only coach in hockey history to accomplish such a feat.

In all, Joe Primeau won the Lady Byng Trophy in 1932, was named to the NHL Second All Star Team in 1934 and played in the NHL All Star Game in 1934. Joe was voted into the Hockey Hall of Fame in 1963.