Horrem has played on a professional level since 1999. He first became Bjørn Maaseide's teammate when Maaseide's former partner Jan Kvalheim retired after the 2000 Summer Olympics in Sydney. Horrem og Maaseide played four seasons together (2001–2004), with four 5. place finishes in the World Tour as their best result. The duo also came fifth in the 2004 European Championships and ended their career together with a 19. place in the 2004 Summer Olympics in Athens.