On 2 August 2018, Østensen signed a six month contract with Viking. He signed a contract extension after the 2018 season.[2] After the 2020 season, his contract expired and he left the club.[3]
In January 2021, Østensen announced his retirement from football,[4] however one month later he returned to his former club Staal Jørpeland.[5][6] On 25 July 2021, he scored a brace against his former club Viking in the first round of the 2021–22 Norwegian Cup, but Staal Jørpeland still lost 3–2.[7]