Physiological adaptions to general stress may affect cell-mediated and humoral responses among dairy cows, with overstocking (OS) and heat stress (HS) serving as 2 common stressors. The objective was to evaluate the effects of OS, HS, and combined OS and HS (OSHS) on delayed type hypersensitivity (DTH) reactions and antibody generation to keyhole limpet hemocyanin (KLH). Intramuscular neck injections (1 mL) containing KLH (0.1 mg), Quil-A adjuvant (0.5 mg), heat killed Candida albicans (HKCA; strain CS5314, 2 × 10⁶ cells) and sterile non-pyrogenic saline were administered on d 2 post-study initiation to 64 cows (parity and days in milk (DIM) ± SEM 1.7 ± 0.1 and 129 ± 8, respectively). To evaluate HS occurrence, cows’ respiration rates (RR) were recorded at 16:00 ± 1 h 4×/weekly. Sera was collected at d 0 before administration and d 7 and 14 post-study initiation. Cell mediated immunity was assed via intradermal injections of 0.1 mL HKCA (d 7: 2 × 10⁶ cells; d 14: 4 × 10⁶ cells) or sterile non-pyrogenic saline in 6 neck spots. At 0, 24, 48, and 72 h post-HKCA administration, DTH was evaluated via calipers. A stimulation index (SI) was calculated as mean HKCA site over mean saline site. The MIXED procedure (SAS 9.4, Cary NC) evaluated the fixed effects of DIM, parity, temperature-humidity index, treatment, d, and time post-injection on SI, antibody generation, and all 2-way interactions. Manual backward elimination removed non-significant 2-way interactions, with all main effects remaining in the model, regardless of significance. Respiration rate was 15 to 16 breaths/min greater among HS and OSHS cows than non-HS cows (P < 0.001), indicating mild heat stress. The SI was greater at 24 h (1.15 ± 0.02) than at 0 h (1.02 ± 0.02, P < 0.001), and equal to 48 and 72 h post HKCA administration, but did not vary between treatments (P = 0.26). Antibody production was not affected by treatment, day, DIM, or parity (P ≥ 0.22). Overstocking, HS, and OSHS did not limit immunity under low doses of antigen, suggesting greater environmental stress and antigen doses may be necessary to trigger response.