Background. - The aim of this study was to compare the effects of the ingestion of either a creatine + guarana (CRE + G) supplement or a placebo (Pl) on muscle power and cognitive performance. Methods. - Seventeen high-level athletes specialized in squash and fencing took part in 2 randomized experimental sessions corresponding to the ingestion of a complex composed by creatine (1000 mg) + guarana (1500 mg) and a placebo. The muscle power was assessed by a test of six maximal sprints on ergocycle sprints: 6 seconds long intercepted by 25 seconds of resting. Cognitive performance was assessed before and after the sprint test using a simple reaction time task, alertness task, ocular motility task and a Go/No-Go task. Supplement was ingested in a two doses, spaced from 30 minutes, 60 and 30 minutes before exercise. Results. - Results indicate a positive effect of creatine + guarana supplement on the muscle power (peak power and fatigue) on and cognitive performance recorded post exercise for alertness Go/No-Go and ocular motricity tasks. No effect was observed on simple reaction time. Conclusion. - Creatine + guarana supplement seems to have a beneficial effect on muscle power and decisional cognitive performance. This result suggests that creatine + guarana ingestion could have an interest to enhance performance in sports with high cognitive constraints. (C) 2015 Elsevier Masson SAS. All rights reserved.