Hailing from Sørum, Karlsen joined regional giants Lillestrøm to play on the highest tier in Norway.
[1][2] Ahead of the 1996 season he joined Vålerenga,[3] winning the 1997 Norwegian Football Cup Final.
In the latter half of 1998 he was loaned to Ikast FS in Denmark, managed by Norwegian Even Pellerud,[4] then to FK Haugesund from March to August 2000.
He made his debut on 4 November 2000 against Bury, and played his last game on 5 May 2001 against Port Vale.
[6] After a period without playing he signed for second-tier club Åsane in Bergen,[7] In 2003 he went on to FK Tønsberg,[8] retiring after the 2004 season and settling in a house in Eik.