The 21-year-old joined Arsenal's academy from Fulham in July 2015 and went on to sign his first professional contract in July 2022.
Sagoe Jr made his senior debut in September 2023 against Brentford in the Carabao Cup. He has also spent time on loan with both Swansea City in the Championship and in League One with Shrewsbury Town last season.
On joining Kalmar, Sagoe Jr said: “It feels great to be here and I am really excited to get started, start training and get to know my new teammates.
“I am looking forward to showing my qualities on the pitch and helping to win matches. This is a good step for me and my continued career.
“After the conversations with the sports director and the management staff, I got a strong feeling that this was the right environment for me.
“Now I want to take advantage of the opportunity and help the team achieve good results.”