This study (60 days) was conducted to investigate the ability of diet enriched with Coriandrum sativum powder or its extract to protect Oreochromis niloticus health and survivability at suboptimal temperature (21 ℃). One hundred and twenty (33.14 ± 0.5 g) were divided into four groups; each group has three replicates.. The first control group fed on a basal diet. Second and third groups fed on diet enriched with 30 mg/kg coriander seed powder (CP) and coriander seed ethanolic extract (CE), respectively. The fourth group (OT) fed on diet enriched with 500 mg oxytetracycline/ kg diet. The results revealed that CE exhibited a considerable improvement in hematological parameters, hepaticrenal functions, antioxidant status, and immunological markers as well as remarkably increased resistance against Aeromonas veronii. It could be concluded that feeding tilapia CE enriched diet at 30 mg/kg is a recommended strategy to enhance tilapia health and resistance to A. veronii infection reared at 21 ℃.