He made his Odense BK debut, starting the whole game, setting up a goal for Hans Henrik Andreasen, who scored twice, in a 2–0 win against FC Nordsjælland on 16 July 2011. Two weeks later on 27 July 2011, Reginiussen scored his first Odense BK goal, scoring from a header, in a 1–1 draw against Panathinaikos in the first leg of the UEFA Champions League third round. In the second leg, he helped the side beat Panathinaikos 4–3, winning 5–4 on aggregate to progress to the next round. However, Reginiussen suffered a muscle injury and had to be substituted in the first half during a 2–1 loss against Aalborg on 13 August 2011. It wasn’t until on 23 August 2011 when he made his return to the starting line-up, as OB lost 3–0 against Villarreal, losing 3–1 on aggregate of the UEFA Champions League Play–Off Round and was eliminated from the tournament. Reginiussen scored his second goal for the club, in a 3–1 win against Wisła Kraków in the UEFA Europa League Group Stage. After missing one match, due to a finger injury, he scored on his return to the starting line-up, in a 3–1 loss against FC Midtjylland on 26 November 2011. Reginiussen later scored again on 25 March 2012, in a 4–2 loss against HB Køge. However, he suffered a leg during a match against FC Midtjylland on 14 April 2012, leading him to be sidelined for the rest of the season. Having established himself in the starting eleven at OB, Reginiussen went on to make thirty appearances and scoring three times in all competitions,