Loob joined Färjestad in 1979 and was a member of the team that won the Swedish championship in 1981. He won the Guldpucken as Swedish player of the year in 1982–83 after setting single-season records of 42 goals and 76 points. He moved to North America following that season to join the Flames, who had selected him with a ninth-round pick at the 1980 NHL Entry Draft. Loob was named to the NHL All-Rookie Team in 1983–84 and in 1987–88 was named a First Team All-Star after becoming the first Swedish player to score 50 goals in one NHL season. He won the Stanley Cup with Calgary the following year, after which he chose to return to Sweden.