The present study was carried out in the agricultural areas of Northwestern Turkey with the purpose to assess the occurrence ofPasteuriaspp. bacteria on plant-parasitic nematodes. The soil samples were collected from olive, cherry, peach, pear, almond, walnut, apple orchards, vineyards, vegetable, and sunflower fields, analyzed and the bacterium was detected on 30 nematode species belonging to 31 families. Nematode individuals fromRotylenchus, Helicotylenchus, Pratylenchus, Tylenchorrhynchus, andGeocenamusspp. were most frequently infected while the average height and width of the spore core and endospore ranged between 3.70-4.90 and 1.40-2.37 mu m, respectively. The results indicated thatHelicotylenchus digonicus,Pratylenchus thornei,P. neglectus,Geocenamus brevidens, Tylenchhorhynchus cylindricus,Rotylenchus cypriensis,Meloidogyne javanica, andM.incognitaindividuals were the most parasitized by the bacterium.