Two experiments were conducted to determine the effects of Cu deficiency with or without high dietary Mo or Fe on the specific immunity of calves. In Exp. 1, calves from 38 bred heifers, fed corn silage-based experimental diets from the last third of gestation until the calves were weaned, were used. Dietary treatments were control (no supplemental Fe, Mo, or Cu), 600 mg of supplemental Fe/kg of DM, 5 mg of supplemental Mo/kg of DM, and 10 mg of supplemental Cu/kg of DM. In Exp. 2, 18 Holstein bull calves were fed commercial milk replacer low in Cu for 49 d and then fed semipurified diets containing approximately 1.1 mg of Cu/kg of DM or diets supplemented with 5 mg of Mo or 10 mg of Cu per kilogram of DM for 126 d. Feeding diets not supplemented with Cu resulted in severe Cu deficiency in both experiments. During Exp. 1, control calves had higher (P < .10) secondary antibody response to pig erythrocytes than Cu-, Mo-, and Fe-supplemented calves. During Exp. 2, in vitro Cu supplementation decreased (P < .01) lymphocyte blastogenic response. In vivo cell-mediated response to phytohemagglutinin was decreased (P < .10) by Cu supplementation during Exp. 1 but was increased (P < .10) by Cu and Mo supplementation during Exp. 2. Copper deficiency and Cu deficiency coupled with high dietary Mo or Fe produced inconsistent immune function responses, indicating that Cu deficiency may not affect specific immune function of calves.