He played junior hockey for the Moose Jaw Canucks from 1947-50 and then played for the Vancouver Canucks (WHL) for four seasons. Popein's rights were bought by the New York Rangers and he played for six seasons (1954-60), centering a line with Dean Prentice and Andy Bathgate. In 1960-61 he rejoined the Vancouver Canucks until the 1967 NHL Expansion when he played one season for the California Seals (1967-68). Popein scored 80 goals and 141 assists in 449 NHL games. He then coached the Providence Reds in 1972-73. He coached the Rangers for part of the 1973-74 NHL season.