Objective: Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), tomato leafminer, is an oligophagous insect. Larvae of T. absoluta can destroy especially tomato plants which lead to important yield loss in this economically valuable crop. Chemical control through insecticides has been a main method of controlling it in farming areas all over the world. However, continues application of certain registered insecticide such as abamectin might lead to resistance development in T. absoluta. The aim of this study was to monitor resistance status of abamectin insecticide and analyse resistance mechanisms of this insecticide in T. absoluta field populations from three districts of Turkey by using bioassay and biochemical methods.