Career
He took over Elfsborg from Magnus Haglund who had been in Elfsborg for 8 years, but moved to be the trainer in Lillestrøm Saskatchewan. He has much knowledge about football and experience as a trainer after 20 years at the sideline. His first player to buy was Joackim Jørgensen from Sarpsborg 08 in Norway, a player as he described was much alike Jari Ilola. He will play in the Europa League Q 2012/13 with Elfsborg.
Lennartsson is former manager of Stabæk, where he started January 2011.
Before Stabæk, he was the manager of the Swedish U21 team after he was held in many positions in various clubs in Sweden, the majority of which were youth coach and assistant manager positions. After the appointment of Erik Hamrén as the head coach of the Sweden national football team there was speculation about Lennartsson being appointed assistant coach.
On August 2, 2010, Stabæk announced that Lennartson would take over as head coach, and replace January Jönsson on January 1, 2011. But only after one season in Stabæk Jörgen had to leave his post as a manager due to Stabæks big economic problems.
Before Allsvenskan season 2012 Jörgen signed a 4-year contract as a head manager foreign
On 30 September 2013, sacked manager Jörgen Lennartsson. Before the start of the 2015 Allsvenskan season, IFK Göteborg appointed Lennartsson as manager following the sacking of previous head coach Mikael Stahre.