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 - Men's beach volleyball|2000 Summer Olympics] in Sydney. Horrem og Maaseide played four seasons together, with four 5. place finishes in the WorldTour as their best result. The duo also came fifth in the 2004 European [Beach Volleyball Championships|2004 European Championships] and ended their career together with a 19th place in the 2004 Summer Olympics - Men's beach volleyball|2004 Summer Olympics] in Athens.
In the winter of 2007, Horrem og Pettersen split up and Horrem challenged Maaseide to a comeback. After some consideration, Maaseide decided to start playing again. The reunited duo made their debut in a World Tour competition in Shanghai, and finished with a thirteenth place.