Potato (Solanum tuberosum L.) is one of the most important vegetable crops in Turkey as well in the world. Potato plants are attacked by a large number of insect pests such as aphids, beetles, leafhoppers and lepidopterous pests under both field and storage conditions. The Colorado potato beetle (CPB) [Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)] and the potato tuber moth (PTM) [Phihorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)] are the most destructive pests in potatoes grown areas. Many pesticides that used to control the potato pests are very toxic to environment and human. An alternative approach to the commercial pesticides is using biological agents like fungi. Purpureocillium lilacinum was described more than a century ago and is a commonly occurring fungus in soil. P. lilacinum (syn: Paecilomyces lilacinus) is the most widely tested fungus for the control of nematodes, aphids and insects. The fungus was determined in Turkey but its molecular identification has not been done yet. In this study, a Turkish isolate of P. lilacinum was identified by classical (morphologic and morphometric properties) and molecular methods. Also, the study concerned with the effect of different conidial concentrations of the fungal isolate on mortality rates of CPB and PTM at different temperatures. P. lilacinum was found to be most effective on the last larval instar of CPB and PTM (33.2 and 43.3% mortality, respectively) on 10th day of treatment with the fungal concentration of 108cfu ml(-1) at 25 degrees C. This fungus developed on all dead larvae and was highly susceptible at the tested temperatures, but its activity decreased at 15 degrees C. Findings of this study showed a potential of the fungus as a bioagent against the CPB and the PTM.