He made his debut in the Continental Cup in February 2005 in Brotterode, scoring two 49th places over two days. His first time among the top thirty occurred in March 2006 in Bischofshofen when he finished 28th, and his first time among the top ten occurred in March 2009 in Trondheim when he finished eighth. He made his World Cup debut in December 2009 in Lillehammer and collected his first World Cup points by finishing 19th. His personal best is 249 meters set in Vikersund on 14 February 2016; the third longest valid jump ever.
He represents the sports club Sprova IL and Trønderhopp, and lives in Levanger.
He is the son of former ski jumper Hroar Stjernen.