Ammar Souayah took the job after Henri Michel stepped down at the end of March.
Michel quit after Tunisia's dismal showing in February's African Nations Cup.
Souayah steered Hamman-Lif to glory in the Tunisian Cup last season, but was meant to be joining as Michel's assistant to gain international experience - only for the Frenchman to leave on the day Souayah began that post.
Working with Souayah will be Khemaies Laabidi who helped the Tunisian youth team triumph at the Mediterranean Games of 2001.