The European grapevine moth, Lobesia botrana ([Denis & Schiffennaller, 1775]) (Lepidoptera: Tortricidae) is one of the most harmful insect pests of grape species in many countries, including Turkey and Iran. The purpose of this study was to determine the bacterial flora and to find a safe and an effective microbial control agent against L. botrana. Bacterial isolates, obtained from larvae of the target insect, were identified using morphological, physiological, biochemical and molecular methods. The insecticidal effects of the bacterial isolates on 3rd and 4th instar larvae of L. botrana were assessed and the results were statistically compared with a control group. The bacterial flora of L. botrana was determined as Enterococcus faecalis (Lb4); Klebsiella pneumonia (Lb6), Enterobacter ludwigii (Lb12, Lb17), Rhodococcus erythropolis (Lb13), Enterobacter aerogenes (Lb15) and Serratia marcescens (Lb21). Bioassay tests showed that the Lb21 had the highest mortality (93%, P < 0.0001) on the larvae of L. botrana within ten days of inoculation. Therefore, S. marcescens Lb21 is a suitable candidate for the development of an effective microbial control agent against L. botrana.