This study aims to understand the effects of cadmium and β-Benzenehexachloride (β-BHC) administered in feed on the physiological response of laying Mallard. Laying ducks (n=120) at three different stages (I: 33-37, II: 38-42 and III: 43-47 weeks old) were randomly allotted into 3x2 factorial design in CRD with 3 Cd and 2 BHC doses, as first and second factor respectively replicated in 4. The doses were doubled (II) and tripled (III) from 0.017 (Cd1), 0.034 ppm Cd (Cd2), and 0.033 ppm β-BHC (P1) of stage I. Hematology, hepatosomatic index (HSI), gonadosomatic index (GSI) and oviductosomatic index (OVI) were compared. At stage I, Cd and β-BHC did not have any significant effects at all parameters observed. Significant effects were observed only at stage II and III. The HSI increased and decreased with 0.033 and 0.067 of Cd treatment, respectively, however β-BHC increased HSI at stages II and III (P<0.05). The OVI was reduced with 0.067Cd, but in combination with 0.067β-BHC it was enlarged (P<0.05). The number of RBC was significantly reduced by β-BHC. The number of WBC was reduced by Cd levels but β-BHC elevated it by 20x10 3 /µl (P<0.05). Percent heterophil was suppressed by Cd but elevated by β-BHC (P<0.05). Lymphocyte was suppressed by 0.1 ppm β-BHC, while monocyte was enhanced by the levels of Cd, but in combination with β-BHC it was reduced (P<0.05). Briefly, HSI, OVI, WBC and heterophil were suppressed by Cd, and lymphocyte and RBC were suppressed by β-BHC. Therefore, individual and low levels of Cd and β-BHC seem tolerable, but in combination their effects are compounded and threaten productivity and food safety. Over-all it is suggested that the combined tolerable limits of heavy metals and pesticide residue should be established for future research and regulatory purposes.All copyrights reserved to Nexus® academic publishers