Abstract: Culex quinquefasciatus is a primary vector of periodic lymphatic filariasis in tropical and subtropical world. In the present study, efficacy of different Insect Growth Regulators (IGRs) such as natural neem product (azadirachtin) and synthetic Chitin Synthesis Inhibitors (CSI) like diflubenzuron, triflumuron and lufenuron have been studied on organophosphate resistant late 3rd-early 4th instar larvae of C. quinquefasciatus belonging to four different geographical locations of India i.e., Jodhpur, Bikaner, Jamnagar and Bathinda and laboratory population. Resistance Ratio (RR) in 50% emergence inhibition (IE50) has been carried out between field populations and laboratory population. Among the IGRs, the CSI (IE50 = 0.0002-0.0006 mg L-1) have been found to be very effective at very low doses in comparison to azadirachtin (IE50 = 0.0171-0.0244 mg L-1). Among CSI, triflumuron was most effective (IE50 = 0.0002 mg L-1) than the others (IE50 = 0.0003-0.0006 mg L-1), indicating no considerable resistance in any larval population against any IGR (RR = 0.6-1.5 folds). The present study indicates high efficacy of these IGRs and suggests use of these IGRs as an effective alternative source of mosquito larval control where insecticide resistance has developed for other conventional insecticides.