Aflatoxicosis is one of the threats that cause severe mortalities in fish farms. The dietary functional additives are a friendly approach attributed to beneficial effects on aquatic animals. The study aimed at evaluating the impact of Spirulina platensis (SP) on the biochemical indices and antioxidative function of Nile tilapia (Oreochromis niloticus) intoxicated with aflatoxin B1 (AFB1). A control diet and 3 test diets were enriched with 0% SP/0 mg AFB1/kg (control), 1% SP (SP), 2.5 mg AFB1/kg diet (AFB1), and 1% SPþ2.5 mg AFB1/kg diet (SP/AFB1). The diets were supplied to three aquaria for each group twice daily at the rate of 2.5% for 30 days. The blood alanine transaminase (ALT), alkaline phosphatase (ALP), and aspartate transaminase (AST) were significantly increased by AFB1 toxicity with regards to fish fed the control and SP diets (P < 0.05). The inclusion of SP in the diet of tilapia intoxicated with AFB1 lowered the levels of ALT, AST, and ALP in comparison to fish contaminated with AFB1 without SP (P < 0.05). The total blood protein and albumin were decreased in fish contaminated with AFB1 (P < 0.05); however, the dietary SP resulted in improving the blood protein and albumin with similar levels with the control and SP diets. The urea and creatinine were increased in tilapia fed AFB1 diet without SP (P < 0.05); however, the inclusion of SP reduced the levels of urea and creatinine with similar levels with the control and SP diets. The antioxidative capacity of Nile tilapia fed SP and contaminated with AFB1 is expressed by superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA) concentration. The activities of SOD and GSH were decreased by AFB1 (P < 0.05); however, dietary SP increased the SOD and GSH in fish fed AFB1. On the other hand, the concentration of MDA was increased in tilapia fed AFB1 (P < 0.05); however, SP decreased the level of MDA in fish fed AFB1. In conclusion, the application of SP in the aquafeed seems to be an innovative approach to relieve the toxic influences of AFB1 on aquatic animals.