Türkiye, is the country of origin of the olive tree and is among the world’s leading olive producers. Most of the olive production in Türkiye is concentrated in Izmir, Aydın, Çanakkale, Balıkesir, Muğla and Bursa Provinces. Bactrocera oleae (Diptera: Tephritidae), being one of the main pests of olive trees, is an important problem in olive cultivation in Türkiye. The efficacy of four Turkish populations of entomopathogenic nematodes against B. oleae pupae was determined under laboratory conditions. They were Steinernema feltiae/12, S. carpocapsae/1133, Heterorhabditis bacteriophora/70, H. bacteriophora/91, which were collected in different regions of Türkiye during our earlier studies. They were tested against the pest by using a single dose at 5 different temperatures (10, 15, 20, 25 and 30 °C). The highest infection rate was observed forH. bacteriophora/91 isolate at 25 °C, and the lowest infection rate was observed for S. feltiae/12 isolate at 10 °C.