Lake Manzala suffers from severe pollution of complex composition from different sources of industrial, agricultural and sewage facilities from the surrounded governorates. The objective of this research was aiming to study the effects of some environmental polluted effluents at five locations of Lake Manzala on the gonads of Oreochromis niloticus. The histological study of testes of O. niloticus showed decreased number of seminiferous tubules with some degenerative changes. They appeared empty from different spermatogenic cells (primary and secondary spermatocytes). Moreover the interstitial cells were collapsed and appeared in all seminiferous tubules. The ovaries presents a deformation from their ideal shapes, thickening and detaching of the membrane of all stages of oocytes and two types of non-bursting atresia in oocytes were markedly appeared. We recommended improving water quality control and the environmental monitoring is essential at Lake Manzala.