Two experiments evaluated the effects of copper (Cu) and zinc (Zn) injection on body weight (BW), body condition score (BCS), pregnancy rate, ovarian traits, and antioxidant and inflammatory responses of beef heifers. In Exp. 1, 29 heifers were assigned to having saline or CuZn (a solution containing 15 and 50 mg/mL of Cu and Zn) subcutaneously injected (5 mL/heifer) 9 days before artificial insemination. Exp. 2 was conducted to increase the statistical power to evaluate pregnancy rate, and 283 heifers were assigned to either the saline or CuZn group. In Exp. 1, CuZn heifers tended (p ≤ 0.10) to gain more BW and to have greater corpus luteum size and plasma concentration of glutathione peroxidase. No effects of treatment were detected (p ≥ 0.18) for BCS; estrus score; serum concentration of Cu, Zn, and cortisol; and plasma concentration of haptoglobin, ceruloplasmin, and superoxide dismutase. In Exp. 2, CuZn heifers had greater (p < 0.01) BW and serum Cu. The CuZn heifers with low BCS had greater (p ≤ 0.05) estrus scores and tended (p = 0.10) to have greater pregnancy rates. Thus, injecting CuZn may be an effective strategy to enhance growth, reproductive performance, and antioxidant responses in heifers, especially when their BCS is below 5.