The purpose of this study was to determine thermoregulatory and cardiovascular effects of wearing men's lacrosse protective equipment during simulated lacrosse activities in the heat. Design: We conducted a randomized, controlled, crossover study. Methods: Thirteen healthy men (22 ± 3 y, 76.2 ± 8.9 kg, 181 ± 6 cm, 16.06 ± 6.16% body fat) completed two matched exercise trials in the heat (WBGT: 25.5 ± 0.8°C). In randomized order, participants donned full men's lacrosse equipment (helmet, shoulder/elbow pads, and gloves) in one trial while the other included no equipment. Participants completed a topography body scan to determine specific body surface area covered with equipment. Rectal temperature (T re ), heart rate (HR), and mean weighted skin temperature (T sk ) were measured throughout trials. Whole body sweat rate was assessed for trial comparisons. Results: The equipment covered 32.62 ± 2.53% body surface area in our participants. Post-exercise T re was significantly greater with equipment (39.36 ± 0.04°C) compared to control (38.98 ± 0.49°C; p = .007). The overall rate of rise of T re was significantly greater with equipment (0.043 ± 0.015°C•min −1 ) compared to control (0.031 ± 0.008°C•min −1 ; p = .041). Regardless of time point, HR and T sk were significantly elevated with equipment compared to control trial (p ≤ .026). Sweat rates were elevated with equipment (1.76 ± 0.74 L•h −1 ) compared to shorts and t-shirt (1.13 ± 0.26 L•h −1 ), but this difference was not significant (p = .058). Conclusions: Our data indicate impairments in heat dissipation and increased cardiovascular strain imposed by men's lacrosse equipment.