Thaumetopoea pityocampa (Den. and Schiff.) (Lepidoptera: Thaumetopoeidae) is an important pest of pine trees in central and southern Europe, including Turkey. This study was conducted in Samsun Province in the Black Sea region of Turkey to identify potential biological control agents of T. pityocampa. Four fungi, Isaria farinosa, Beauveria bassiana, Fusarium sambucinum and Aspergillus terreus, were isolated from T. pityocampa larvae collected from pine forests. To determine their efficacy against T pityocampa larvae, an experiment was conducted against fourth instar larvae under laboratory conditions. Three application methods, spraying, dipping and residue were used, with suspensions of 108 spores/ml. There were differences among the efficacies of the fungi. The I. farinosa isolate had the highest efficacy, with 55% and 51% for the dipping and residue methods, respectively, followed by the B. bassiana isolate (31% and 15%). The efficacies of the F. sambucinum (24% and 8%) and A. terreus isolates (5% and 1%) Were low. The isolates of I. farinosa and B. bassiana were determined to be potential biological control agents of T. pityocampa.