Stress is how the human body adapts when, repeatedly exposed to exercise and/or environmental conditions, it exceeds its initial capacities and adapts. However, when they are not controlled, these extreme environmental constraints, such as high temperatures sometimes coupled with high hygrometry, amplify the stress imposed on the body and expose individuals to significant decrements in performance and increased health risks. A better understanding and management of environmental constraints is therefore a major challenge for athletes, workers, and their support crew. While the physiological responses to extreme environments have benefited from a large body of literature, their influence on psychological functioning is less understood. In this special issue, four articles focus on the psychological perceptions, cognitive performance and athletic performance of individuals subjected to harsh environments (tropical conditions, hypoxia, passive hyperthermia). While a first study measured the impact of a constraining thermal condition (i.e., passive hyperthermia) on the cognitive functioning of individuals, the other three studies focused on possible interventions (self-selected motivational music, per-cooling, motivational strategies) to help individuals perform under environmental stress conditions (hypoxia and/or tropical conditions).