Slim Halderson began his career with the Manitoba Hockey League in 1917-18. Between then and 1920, he played for two Allan Cups and represented Canada in the 1920 Olympics with the Winnipeg Falcons. He then logged a season each with the Saskatoon Crescents and the Victoria Aristocrats before donning the Victoria Cougars sweater. He was a member of that club from 1922-23 until 1925-26. During his stint there, he was a part of the Stanley Cup-winning team of 1924-25. The following year he helped the Vics defend their title against the Montreal Maroons, eventually losing in four games.
Halderson arrived in the NHL when Detroit purchased the Victoria Cougars during the 1926-27 season. He played for the Detroit Cougars in 19 games and the Toronto Pats and Leafs in 25 more, having been traded by Detroit for Pete Bellefeuille. He then spent two seasons in the Canadian-American Hockey League before moving on to the American Hockey Association, where he played until 1937.