Johnsson won the SHL's Le Mat trophy championship with Skellefteå AIK in 2024.
Jonathan's younger brother Andreas is also an ice hockey player, currently also playing for Skellefteå AIK.
During the 2007–08 season Johnson played one game for Kings' senior team in Division 3—Sweden's fifth highest league.
In 2008 Johnson represented Halland in TV-pucken, collecting two assists in five games, the same year he also joined Frölunda's junior organisation for the 2008–09 season.
In the Swedish U18 Championship playoffs Johnson production dropped, scoring one goal and three points in eight games as Frölunda won a bronze medal.