BACKGROUND: Creatine supplementation has some beneficial effects on cognitive processing in healthy adults, including athletes; however the effects on cognitive function following exhaustive exercise in athletes is unknown. Therefore, the purpose was to determine the effects of 28 days of creatine supplementation on tasks of cognitive performance immediately following exhaustive exercise in Muay Thai female athletes compared to placebo. METHODS: Using a repeated measures, double-blind, placebo controlled design, 26 female Muay Thai athletes (age: 26 ± 5 years; body mass: 65.1 ± 6.6 kg; height: 162 ± 5 cm; training experience: 2.6 ± 0.6 years) were randomized to supplement with creatine monohydrate (3 g/day) or placebo (maltodextrin) for 28 days. Prior to and following supplementation, measures of cognitive performance were assessed (visual and auditory reaction time, corsi block test, visual forward digit span, and Erikson Flanker Task) immediately after exercise. RESULTS: There was a time main effect for auditory reaction time (p = 0.035), with no differences between groups. There was a trend for an interaction effect for visual reaction time (p = 0.067), visual go-no-go reaction time (p = 0.087), and Erikson Flanker task (p = 0.06), with exploratory post hoc tests revealing improvements over time in the creatine group (p \u3c 0.05) with no changes in the PLA group (p \u3e 0.05). CONCLUSION: Twenty-eight days of creatine supplementation appeared to have a small but positive effect on cognitive performance following exhaustive exercise in female Muay Thai athletes. Future research using a larger dose over a longer duration is warranted