keep four clean sheets between 8 April 2018 and 29 April 2018; during which, he scored in a 2–0 win against IK Start. Since the start of the 2018 season, Reginiussen continued to regain his first team place, playing in the centre–back position, forming a partnership with Even Hovland. A month later on 30 May 2018, he scored the winning penalty for Rosenborg, as they beat Odds 7–2 in the shootout after the game went to extra time, with a 2–2 scoreline. Two months later on 11 June 2018, he scored his second goal of the season, in a 2–1 loss against Tromsø. This was followed by helping the club keep two clean sheets in the next two matches against Vålerenga and Sandefjord. Reginiussen helped the side qualify for the UEFA Europa League Group Stage after beating KF Shkëndija 5–1 on aggregate; in which he scored in the second leg. In a match against IK Start on 11 November 2018, Reginiussen started the match and helped them to keep a clean sheet, as they won 1–0, a victory that saw the club become Champions for the fourth time in a row. In a follow–up match against Bodø/Glimt, he set up a goal for Yann-Erik de Lanlay, as they drew 1–1. A month later on 2 December 2018, Reginiussen started the match, as he helped the side beat Strømsgodset win 4–1 win to win the tournament, his third time of his career. Reginiussen scored his fourth goal of the season, in a 1–1 draw against RB Leipzig on 13 December 2018. At the end of the 2018 season, he went on to make forty–seven appearances and scoring four times in all competitions. In the 2019 season, Reginiussen continued to regain his first team place, playing in the centre–back position and forming a partnership with Hovland. He scored his first goal of the season, in a 3–1 loss against Stabæk on 14 April 2019. His second goal then came on 19 May 2019, in a 3–2 win against Mjøndalen IF. A month later, he captained the side for the first time since 2016, as Rosenborg lost 1–0 against Tromsø. Three days later, Reguiniussen scored an equalising goal in a 1–1 draw against Aalesund in the Round of 16 of the Norwegian Cup; which the club lost on penalty shoot–out. It was announced on 1 August 2019 that Reginiussen signed a contract with