A 3-week-feeding study (1–21 d post-hatch) was conducted to evaluate the efficacy of total curcuminoids (TCMN), as an antioxidant, to ameliorate the adverse effects of aflatoxin B1 (AFB1) in broiler chickens. Turmeric powder (Curcuma longa L.) that contained 2·55 % TCMN was used as a source of TCMN. Six cage replicates of five chicks each were assigned to each of six dietary treatments, which included: basal diet; basal diet supplemented with 444 mg/kg TCMN; basal diet supplemented with 1·0 mg/kg AFB1; basal diet supplemented with 74 mg/kg TCMN and 1·0 mg/kg AFB1; basal diet supplemented with 222 mg/kg TCMN and 1·0 mg/kg AFB1; basal diet supplemented with 444 mg/kg TCMN and 1·0 mg/kg AFB1. The addition of 74 and 222 mg/kg TCMN to the AFB1 diet significantly (P < 0·05) improved weight gain and feed efficiency. Increase (P < 0·05) in relative liver weight in birds fed AFB1 was significantly reduced (P < 0·05) with the addition of 74, 222 and 444 mg/kg TCMN to the AFB1 diet. The inclusion of 222 mg/kg TCMN ameliorated the adverse effects of AFB1 on serum chemistry in terms of total protein, albumin and γ-glutamyl transferase activity. The decreased antioxidant functions due to AFB1 were also alleviated by the inclusion of 222 mg/kg TCMN. It is concluded that the addition of 222 mg/kg TCMN to the 1·0 mg/kg AFB1 diet demonstrated maximum antioxidant activity against AFB1.