This study aimed to investigate the larvicidal activity and inhibition effect of Sea lettuce Ulva lactuca extracts using various organic solvents (acetone, ethanol, and petroleum ether), against mosquito larvae of Culex pipiens (L.). The results revealed that all the extracts showed varied levels of larvicidal activity and inhibition effect against C. pipiens. Among them, the maximum efficacy was observed in the acetone extract which resulted in the strongest inhibition effect in the adult emergence (95%) and showed larvicidal activity (LC₅₀=5.004 and LC₉₀=9.76 mg/ml). Moreover, the three extracts of U. lactuca caused a reduction in the egg-laying capacity of mosquito females. Besides, the acetone extract caused the highest decrease (P < 0.05) on the mean number and hatchability of eggs produced by mosquito females. Thus, the present study suggested that using acetone, ethanol, and petroleum ether extracts of U. lactuca could be an effective method, somewhat easier, safe, and less expensive for controlling C. pipiens mosquito.