She played for Bälinge IF and Umeå IK in the Swedish Damallsvenskan and spent time with San Diego Spirit and Carolina Courage while contracted to Women's United Soccer Association (WUSA) in 2001.
She would train with her local Swedish Football Division 5 male team and commute to Bälinge, more than a hundred miles away, for matches.
[5] The move to Carolina was not a success, as Karlsson was unable to dislodge Kristin Luckenbill from the starting goalkeeper position.
[7] She played in the UEFA Women's Cup quarter-final defeat to Djurgården/Älvsjö, making "a string of fine saves" as holders Umeå lost their title.
At the 1996 Atlanta Olympics Karlsson made a substitute appearance in the Swedes' final group game, a 3–1 win over Denmark, when starting goalkeeper Annelie Nilsson was inadvertently injured by Lena Videkull's elbow.