Karimi replaced Faraz Kamalvand, who resigned from his post on Thursday.
Karimi led Tractor as Rasoul Khatibi’s replacement at the end of the last season and the Tabriz-based football team finished in fourth place under coaching of the long-serving coach in Iran Professional League.
Tractor is to meet Al-Nassr of Saudi Arabia in the AFC Champions League Round of 16 on Tuesday.
The match will be held in Doha’s Jassim Bin Hamad Stadium.