He grew up in the little hamlet of Aurskog in eastern Norway and represented the local sports club Aurskog-Finstadbru SK.

His biggest success at the 1994 Winter Olympics in Lillehammer where he earned a silver medal in the Individual Normal Hill.

Ottesen also finished 4th at the 1995 Nordic skiing World Championships in the Individual Large Hill.

Lasse is now Nordic combined director in the International Ski Federation (FIS).

In the 1993/94 Four Hills Tournament, Ottesen was accused of helping his compatriot Espen Bredesen beat German Jens Weißflog.