Tomato fruit borer (Helicoverpa armigera Hübner) is a polyphagous pest that negatively affects yield and quality in tomato cultivation, and its importance has increased between the harmful species with the increase in population density in recent years. In this study, population monitoring of tomato fruit borer was carried out in the Central, Çınar, Ergani, and Bismil districts of Diyarbakır province in 2013 and 2014. The plants were randomly selected to represent the field at each location, starting from the seedling period to harvest until the adult and immature stages of pests were followed weekly. The highest infestation rates of immature stages were determined at Central and Ergani districts in September and October as 80%, while the highest numbers of adults were caught in Bismil district in August as 237 individuals/trap. Apanteles sp., Habrobracon sp., Campoletis sp., and Hyposoter sp. were found as larvae parasitoids of H. armigera. The parasitization rate of larvae was determined as 2.04% in the first year, while it was found as 1.53% in the second year. Species such as Deraeocoris pallens (Reuter, 1904), Macrolophus pygmaeus (Rambur, 1839), Geocoris pallidipennis (A. Costa, 1843), G. megacephalus (Rossi, 1790), Nabis pseudoferus (Remane, 1949), Orius niger (Wolff, 1811), O. albidipennis (Reuter), Chrysoperla carnea (Stephens, 1836), Adonia variegata (Goeze, 1777), Coccinella septempunctata (Linnaeus, 1758) and Scymnus levaillanti (Mulsant, 1850) were determined as predators of the pest. According to the findings of this study, infestation and population density of H. armigera may be affected due to chemical applications and natural enemies as well as climatic conditions in Diyarbakır province.