Two months feeding trial was conducted to evaluate the role of chia seed powder (CSP) enriched diets in improving Oreochromis niloticus tolerance to cold thermal stress. A total of 200 Nile tilapia fish were divided into 5 experimental groups with 4 replicates (10 fish/ replicate). Experimental groups were fed on the basal diet (BD) supplemented with CSP at levels 0.0, 1.5, 3, 4.5 and 6 g/ kg diet and reared at 16–19 ◦C temperature range. Fish growth performance (final weight, total gain, and specific growth rate) was linearly increased with increasing dietary CSP supplementation (linear, P < 0.0001) along with improved FCR compared to the control. The highest survival rate was recorded in tilapia which received 6 g chia /kg diet. Dry matter (DM) and crude protein (CP) % of fish whole body were increased (linear response, P = 0.009, P < 0.0001, respectively), while ash and crude lipids % were reduced in CSP-supplemented tilapia (linear, P = 0.0008, P = 0.0186, respectively). A linear increase in red blood cells (RBCs), white blood cells (WBCs) counts and hemoglobin (P < 0.0001) of fish was also achieved with increasing chia level. The serum lipid profile parameters, glucose and cortisol levels in Nile tilapia fish under cold stress tended to decrease in response to increasing chia powder level (linear, P < 0.0001). Serum antioxidants (total antioxidant capacity-TAOC, reduced glutathione-GSH and catalase-CAT) and immune response parameters concentrations (IgM, IgG and lysozymes) were significantly improved with supplemental CSP added in diet reared under cold stress. In conclusion, dietary inclusion of chia seed powder (optimum level 4.5 and 6 g/ kg diet) in Nile tilapia raised under lower temperature (16–19 ◦C) showed a stress relieving effects through increasing their survival rate, enhanced growth performance, antioxidants, immunological responses and reducing the stress related indicators as cortisol