Two hundred and fifty Japanese quail chicks, seven days old without sexing were used in this study to investigate cadmium's harmful impacts on performance and immunological parameters, as well as their regulation by various levels of milk thistle plant seed powder (Mthsp)in growing quail. The quails were separated into five equal groups, each with 50 chicks, and each group was assigned five replicates (10 each). Group 1 served a basal diet with no supplements (T1), group 2, fed 0.10 g cadmium chloride/kg diet (T2), groups 3, 4, and 5 fed on 0.10 g cadmium chloride/kg diet supplemented with either of 4, 8 and 12g (Mthsp)/kg diet, respectively. Cd caused a significant (P ≤ 0.01and 0.001) increase in white blood cell (WBCs) count and a decrease in hemoglobin (HGB) and a numerical decrease in packed cell volume (PCV) as compared with those of the control free of Cd supplementation. While a nonsignificant decrease in red blood cell (RBC) count was detected. Cd intoxicated quail had a nonsignificant (P ³ 0.05) reduction in serum catalase, and a significant (P ≤ 0.05) decrease in total antioxidant capacity, although MDA was significantly (P ≤ 0.01) elevated in contrast to the control group. These results mean that dietary supplemented with (Mthsp)/kg diet might be useful on performance, and hematological parameters induced by Cd and alleviated the adverse effect of Cd on antioxidative.