In this study, the efficacy of Turkish isolates of four entomopathogenic nematodes (EPNs) against the last instar larvae of the potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae) were investigated under laboratory conditions. Potato moths were collected from infested potato fields in Derinkuyu (Nevşehir Province) in June 2019. The four EPN species used were Steinernema affine Bovien, S. carpocapsae Weiser, S. feltiae Filipjev and Heterorhabditis bacteriophora Poinar. Efficacy experiments were carried out in 9 cm diameter plastic Petri dishes with doses of 50 IJs / larva at 25 o C. Mortalities were recorded after 24, 48, 72 and 96 hours. The mortality of P. operculella larvae caused by EPN species increased over time. From 24 h to 96 h, mortality increased from 40% to 66.6%, 83.3% to 100%, 93.3% to 100% and 96.6% to 100%, respectively. On the second day after S. feltiae application, there was 100% mortality of the pest larvae. All EPN species used in the experiment caused time-dependent, high mortality of P. operculella larvae. These promising results for the efficacy of four Turkish EPN isolates against the major potato pest, P. operculella warrant detailed field investigations of their potential use for the control of this pest in commercial potato production.