He represented Hammarby IF during his whole playing career and later went on to coach the club for 18 years, as the longest-serving manager in its history.

In 1940, Hammarby played one season in Allsvenskan, the domestic top league, but was relegated immediately.

The next season, Adamsson took over as head coach of Hammarby, replacing Sven Bergqvist.

[8] Up on his return to Hammarby, Adamsson said:[1] I had been away for a while and knew the club was in a downward spiral: no players, no coaches, no finances, everything seemed to be falling apart.

[10] Hammarby went on to compete in Allsvenskan during the majority of Adamsson's stint at the club, before he decided to step down as manager at the end of 1965, being replaced by Georg Kraemer.