Investigations on “Efficacy of synthetic and biopesticides against thrips, (Scirtothrips dorsalis Hood) in chilli” were carried out at Samajik Vigyan Kendra, Dr. B. R. Ambedkar University Rehti, (Village Bordi) Tehsil- Nasrullaganj, Distt- Sehore (M.P.) during Rabi, 2018-19 and 2019-20. A total of ten treatments including untreated control was taken to test their efficacy. Based on the mean per cent reduction in thrips population in all three sprays the treatment of fipronil (77.48%), was found to be the most effective, followed by spinosad (73.53%), emamectin benzoate (71.99%), thiamethoxam (70.23%) former three treatments were statistically at par with each other in their efficacy. The treatments of carbosulfan 25 EC (67.09%), propalgite 57 EC (66.57%), neem (65.10%) and fenpropathrin 30 EC (64.78%) percent reduction, formed a moderately effective group of insecticides. The minimum reduction was noticed in bifenthrin 10 EC (58.65%). The highest fruit yield of 106.26 q ha-1 was recorded in the plots treated with fipronil, followed by thiamethoxam (104.20 q ha-1), emamectin benzoate (100.35 q ha-1), spinosad (98.11 q ha-1). The lowest fruit yield was recorded in the plots treated with neem (56.95 q ha-1) followed by bifenthrin (60.50 q ha-1). The maximum cost-benefit ratio of 1:2.98 was recorded in the treatment of fipronil, followed by thiamethoxam (1:2.91), emamectin benzoate (1:2.79) and spinosad, (1:2.72). The cost-benefit ratio of 1:2.38, 1:1.87, 1:1.61, 1:1.49, and 1:1.43 were recorded in the treatments of fenpropathrin, carbosulfan, propelgit, bifenthrinand neem respectively. The descending order of insecticides effective in controlling this pest and their order of efficacy was fipronil> spinosad>emamectin benzoate> thiamethoxam>carbosulfan>propalgite> neem>fenpropathrin& bifenthrin.