The aim of this study was to determine the preventive efficacy of black seed (Nigella sativa L.), thymoquinone and Na bentonite on biomarkers of tissue degeneration in the liver and other organs induced by aflatoxin (AF) in broilers. One hundred broiler chicks were divided into 10 equal groups and fed for 28 days. The animals received feed with 2 mg/kg total aflatoxin, Nigella sativa (NS; 5%), thymoquinone (TMQ; 300 mg/kg) and Na bentonite (BNT; 10 g/kg) both individually and in combination. At the end of the experiment, blood and liver tissue samples were collected. AF treatment significantly increased serum and liver 8-hydroxy-2’-deoxyguanosine(8-OHdG), serum transforming growth factor β (TGF-β), and liver total antioxidant capacity (TAC) levels, whereas it significantly decreased liver TGF-β and serum TAC levels compared to the control. However, there were no changes in the serum and liver hepatocyte growth factor (HGF) levels from AF. Both individual and combined addition of NS, BNT and TMQ to AF-contaminated feed significantly improved liver 8-OHdG, liver TAC and serum TGF-β levels. Serum 8-OHdG levels were ameliorated only in the AF+BNT+TMQ group. In addition, the AF+BNT+NS and AF+BNT+TMQ groups showed significant improvement in liver 8-OHdG, liver TGF-β and liver TAC levels. We conclude that NS and TMQ supplementation to AF-contaminated feed may be beneficial against aflatoxicosis in broilers.