2003-04: Johan Harju scored 14 goals with 12 assists in 35 games for Lulea's U-20 team in Sweden.
2004-05: Harju made his first appearance in the Swedish Elite League – playing four games with Lulea. He spent the majority of the season with Lulea's U-20 team and scored 18 goals with 13 assists and 14 PIM. Harju represented Sweden at the U-19 and U-20 levels and scored two goals in seven international matches but did not play at the WJC tournament.
2005-06: Harju split the season between the SEL and U-20 with Lulea. He scored 3 goals with 1 assist and 8 PIM in 39 games with the men's team and scored 14 goals with 9 assists and 4 PIM in 17 games at the junior level. Harju was scoreless in four SEL playoff games and had 3 goals with 1 assist in four playoff games for the junior team.
2006-07: Harju established himself as a full-time pro as a 20-year old with Lulea, playing 55 games in the SEL and also playing two matches for Sweden's national team in the European Hockey Tournament. Harju scored 12 goals with 10 assists and 30 PIM and added two goals in four playoff games for seventh-place Lulea. Harju scored 2 goals with 1 assist for Team Sweden.
2007-08: After being drafted by the Lightning the previous summer, In Harju scored a career-high 20 goals, tops on the team for Lulea. He added 8 assists and 55 PIM in 51 games though Lulea slipped to 10th in the 12-team league. Though there were rumors he would join Tampa Bay's AHL affiliate Norfolk following the SEL season, they proved to be unfounded.
2008-09: Harju broke out offensively for Lulea, which had its first winning season since 2004-05 and finished in fifth place. Harju's 27 goals tied him for second in the SEL with HV71's Martin Thornberg and he added 22 assists and was +13 with 30 PIM in 55 games. His 49 points were second to Linus Omark (55) on Lulea. Harju was lethal on the power play, scoring 10 of his 27 goals with the man advantage. In five playoff games, he scored 4 goals with 1 assist. Harju was a regular with Team Sweden both in the European Hockey Tournament and at the World Championships. He scored 2 goals with 2 assists and 4 PIM in nine games at the World Championships. Harju signed a contract with Dynamo Moscow of the KHL in April.
2009-10: Johan Harju spent much of the season playing center for Dynamo Moscow after being a wing for most of his career. While his offensive numbers were down, Dynamo was one of the top teams in the KHL finishing sixth in the 24-team league. Harju scored 4 goals (two on the power play) with 14 assists and was -10 with 38 PIM. In the KHL playoffs, he scored 1 goal and was -2 with 8 PIM in two games. Harju played for Team Sweden at the World Championships and scored 4 goals with 1 assist in nine games as Sweden won the Bronze Medal. Harju signed a two-year, entry-level contract with the Lightning in April.
2010-11: Harju made his NHL debut with the Lightning in November and appeared in ten games with Tampa Bay; spending most of his first season in North America with the Lightning's AHL affiliate in Norfolk. Harju scored 1 goal with 2 assists and was -2 while averaging 8:28 minutes of ice time per game with Tampa Bay. Harju was the third-leading scorer for the AHL Admirals with 23 goals and 29 assists in 63 games and was +15 with 20 PMs. He skated in all six playoff games for Norfolk and scored 1 goal with an even plus/minus and 6 PMs. Harju signed a contract with Lulea in the Swedish Elitserien in April 2011.
Harju is first and foremost a goal-scorer. He is a strong and powerful winger with good size and good balance on his skates. He showed his versatility by playing center in the KHL, albeit with mixed results. Harju is a good finisher, both from tight spots low in the zone and with an accurate shot and quick release from the slot or the top of the circles. He has well-rounded technical and puckhandling skills combined with mature hockey sense, anticipation and vision. He is not the fastest skater, but has improved in that area since his junior days. His size should allow him to compete in the more combative, tighter checking style of play in NOrth America - though he has yet to face the calibre of defense he will see at the NHL level.
Harju has returned to Sweden to play for Brynas IF in 2013-14.