Exposure of the Nile tilapia (Oreochromis niloticus = O. niloticus) to dry powder suspension of Anagallis arvensis (A. arvensis) at concentrations of 50 ppm and 100 ppm for 24 and 48 hours was under consideration for studying the reaction of this fish against the used plant. A. arvensis was previously succeeded as an effective molluscicide for control of Schistosoma and Fasciala snails. The present study aimed to test the effect of the molluscicidal doses of Saboon El- Gheit (A. ar- vensis) on some serum parameters and some tissue histopathological observations of O. niloticus to clarify whether this plant is safe, non toxic and fit for this type of fish or not. O. niloticus which were brought from Bahr Muess at Zagazig City to the working place where, they were acclimatized and exposed to the plant suspension showed no clinical symptoms and no patho-anatomic signs externally or internally after exposure periods and at sampling. However, the estimated levels of serum parameters in the studied fish: glucose, total lipid, total protein, total albumin, globulin, albumin/globulin ratio (A/G), uric acid, urea and creatinine showed no significant changes after 24 and 48 hours of exposure in comparing with controls. Whereas, serum enzyme activities of amino transferases (aspartate aminotransferase = AST and alanine aminotransferase = ALT) and alkaline phosphatase (AP) in addition to values of serum electrolytes (Ca++, P++ Mg++, Na+, K+. and K+/Na+ ratio) presented insignificant deviations at the same periods of sampling. Although, there are some slight deviations in some above measured parameters, but they are non signifi- cant. The histopathological examination of gills, liver, spleen and skeletal muscles of O. niloticus in the present research exhibited non-significant lesions at the time of sampling. Therefore, all above results revealed that the dry powder suspension of A.arvensis a molluscicidal concentrations has neither toxic nor hazard effects for O. niloticus all over the conditions of this study.