Ahead of the 2013 season, Reginiussen was chosen by the new head coach Per Joar Hansen as Rosenborg's captain, replacing Mikael Dorsin. He started the season well as captain by helping the club keep a clean sheet in the first three league matches of the season. Reginiussen started the first seven matches until he was sent off in the 65th minutes for a professional foul in a penalty box. In a 1–0 loss against Sandnes Ulf on 28 April 2013. Having served his suspension, Reginiussen returned to the starting line-up, in a 2–1 win against Tromsø on 8 May 2013. He scored his first goal of the season, scoring from a header, in a 2–1 win against Vålerenga on 25 May 2013. Reginiussen then followed up in the next three matches by keeping a clean sheet. He scored three goals throughout August, scoring against Sogndal IL, Strømsgodset and Sandnes Ulf. Reginiussen helped the side finished second place after Strømsgodset won their match on the last game of the season, with performance earned attention from the Norwegian media. In the Norwegian Football Cup Final against Molde, he scored the club’s second goal of the game, as they lost 4–2. At the end of the 2013 season, Reginiussen went on to make thirty–seven appearances and scoring five times in all competitions.