Overstocking (OS) and heat stress (HS) are 2 primary management challenges impacting dairy cow welfare. The objective was to evaluate the effects of a single stressor, OS or HS, or concurrent dual stressors (OS and HS; OSHS) on behavior and milk production of lactating dairy cows. A 4 × 4 Latin square was implemented on 64 cows (parity and days in milk (DIM) ± SEM; 1.7 ± 0.1 and 129 ± 8, respectively) housed in sand freestalls and milked 2×/d during summer 2017. Each period included a 7 d acclimation and 7 d of data collection. Respiration rate (RR) was recorded at 16:00 ± 1 h 4 ×/weekly and vaginal temperature (VT) was collected via blank CIDR and Ibutton (Embedded Data Systems, Lawrenceburg, KY) on 6 cows/pen, to determine cows’ heat stress. Pen temperature humidity index (THI) was recorded during all periods. A subset of cows (n = 11/pen; parity and DIM ± SEM; 1.5 ± 0.8 and 122 ± 39, respectively) were equipped with accelerometers. The MIXED procedure (SAS 9.4, Cary NC) evaluated the fixed effects of DIM, parity, treatment, and THI on lying time, steps/d, milk production, and all 2-way interactions, blocked by pen and period. Manual backward elimination removed non-significant 2-way interactions, with all fixed effects remaining in the model, regardless of significance. Respiration rate was 14 to 16 breaths/min greater among HS and OSHS cows than non-HS cows (P < 0.001), and VT was equal between treatments (P ≥ 0.73). Elevated RR suggested cows experienced mild HS without modifying VT. Primiparous OSHS cows lay 51 and 71 min/d less than OS and HS cows, respectively (P < 0.003). Overstocked and OSHS cows took 186 and 193 more steps/d than cows exposed to no induced stressor (P < 0.002), suggesting more displacements and standing time among OS cows. Heat stressed and OSHS cows produced 1.7 ± 0.8 and 2.1 ± 0.8 kg/d (P < 0.001) less milk than non-HS cows. Despite short duration of treatments, behavior and milk production were influenced by individual stressors, with no greater effect on cows exposed to dual stressors. We hypothesize prolonged dual stressors may be more detrimental to animal behavior and production.