Aflatoxin B1 is one of the most important mycotoxins due to its hepatotoxic and carcinogenic effects on some fishes. This study was conducted to investigate the defensive role of curcumin and garlic on phase I of the biotransformation system in the liver of aflatoxicosis in Oreochromis niloticus in relation to the therapeutic properties by studying hepatic histopathology and cytochrome P450-CYP1A gene expression using real-time polymerase chain reaction (RT-PCR). Although varieties of methods have been used for gene expression quantification and are still used today, real-time RT-PCR method has achieved prominence in recent years. One hundred and eighty (180) fish were equally divided into 10 groups. T1 was the negative control; fish in T2 were injected intraperitonealy (IP) with AFB1 at a rate of 6 mg kg -1 B.W. and fed on a basal diet. Groups T3-T6 were fed with garlic (T3 & T4) and curcumin (T5 & T6) at 10 & 20 g kg -1 diet, respectively. Groups T7-T10 injected IP with AFB1 and fed on both garlic and curcumin at the different concentrations (10 & 20 g kg -1 diet). AFB1 reduced the HSI values in aflatoxicosis fish. Feeding a low dose of garlic led to significant improvement in the HSI values. Histologically, hepatic lesions were observed in the AFB1 injected groups; damage was reduced when fish were fed on garlic and curcumin diets at a concentration 10 g kg -1. The highest induction of CYP1A expression was observed in the curcumin groups followed by AFB1. The over expression of CYP1A in T2 was alleviated by the garlic. Therefore, it was found that garlic enhances the detoxification of AFB1 through the suppression of CYP1A in the liver.