After joining Aalesund's first-team squad, the young Grytebust was the third-choice goalkeeper behind Adin Brown, Andreas Lie and later Anders Lindegaard who joined the side on loan. In August 2009, after Lindegaard's loan-spell ended the team's coaching staff decided to give Grytebust his first team debut in place of Lie. He made his debut against local rivals Molde FK on 22 August 2009, and delivered a good performance despite conceding three goals. After his debut, Aalesund signed Lindegaard permanently and Lie left the team, leaving Grytebust as the second-choice goalkeeper for the following season. He played in the two first rounds of the 2010 Norwegian Football Cup.