Information on the effects of heat stress on cognitive function remains largely equivocal despite substantial number of studies conducted in the area (Gaoua, 2010). Recent evidence has shown that cooling the neck region can enhance endurance performance (Tyler et al., 2010; Tyler and Sunderland, 2011). There is however limited information about the efficacy of cooling the neck region on cognitive performance. The objectives of this study were to assess the effect of exercise-induced hyperthermia and the efficacy of a neck cooling collar on cognitive performance. Prior to the experimental trials, 12 healthy males (age: 24±2 (mean±SD) years; peak oxygen uptake: 59±5 ml/min/kg) undertook three practices of a battery of five cognitive tests (symbol digit matching, search and memory, digit span, choice reaction time and psychomotor vigilance) at different days and a full familiarisation trial. Following which they completed two experimental trials (no-collar: NC and cooling collar: CC) separated by at least a week using a counter-balanced design. On each of these trials, they were required to run on a treadmill at 70% of their peak oxygen uptake for 75 min under a warm and humid condition (dry bulb temperature: 30.2±0.3°C, relative humidity: 71±2%). Cognitive performance was assessed before and after the exercise. Body core temperature, neck and mean skin temperatures (chest, arm, thigh and calf), heart rate, rating of perceived exertion and thermal sensation were measured. Body core temperature was substantially elevated at the end of the runs (NC: 39.5±0.4 vs. CC: 39.6±0.3°C, p>0.05). Neck temperature was lower in the CC trial (26.0±3.6°C) than in the NC trial (36.0±0.6°C, p<0.001). Neck cooling had no effects on other physiological and subjective responses (p>0.05). Exercise-induced hyperthermia improved mean reaction time in the Symbol Digit Matching test (pre: 1624±79 vs. post: 1490±232 ms, p<0.05). After the run, maximum span was increased in the Digit Span test (pre: 10±2 vs. post: 11±2, p<0.05) and median reaction time was improved in the Psychomotor Vigilance test (pre: 262±55 vs. post: 244±46 ms, p<0.05). Exercise-induced hyperthermia had no effects on the Search and Memory and Reaction Time Choice tests (p>0.05). Application of a neck cooling collar reduced the number of search errors made in level 3 of the Search and Memory test (NC: 0±1 vs. CC:-1±2; p<0.05). Wearing a cooling collar had no effects on the other tests (p>0.05). These results suggest that, with prior practices of cognitive tests, exercise-induced hyperthermia can improve memory and behavioural alertness. The benefits of wearing a neck cooling collar may only occur during tasks of higher complexity.