Abstract:In controlling eutrophication phenomenon, there were conventional methods which lead to negative effects to aquatic environment. This study was aimed to investigate the usage of synthesized thiourea compounds to inhibit the growth of Oscillatoria sp. in Kenyir lake, Terengganu, Malaysia. The inhibition effects of four eco-friendly alkoxyl thiourea derivatives compounds named as N- ((4 as an algae inhibitor. However, extensive studies still need to be conducted in order to investigate the mechanism on how this compound reacts with Oscillatoria sp..