 On 10 January 2018, Billborn took over as manager of Hammarby IF in Allsvenskan, signing a three year contract.He led the club to a surprising 4th position in the table during his debut season, after being placed first in the league mid-season.In 2019, Hammarby started the league play in a mediocre fashion, but made a strong finish to the season (with eight straight wins during between match day 22 and 30) and ultimately finished 3rd in Allsvenskan.