Introduction: Rice germ (RG) could be a safe and effective dietary supplement for swimmers. Methods: This randomised, parallel, placebo controlled pilot study investigated the effect of a five-week RG supplementation (25 grams/two times/day) in moderately trained swimmers on 50-m and 200-m front crawl at maximal speed, as primary outcome, and body composition, muscle function, post-concussion assessment, cognitive testing (ImPACT) and lactic acid levels, as secondary outcomes. Twenty seven moderately trained swimmers (7 women and 20 men) participated in the study. Results: For primary outcome on 200-m front crawl at maximal speed, a significant average decrease of 2.98 seconds (p=0.022) was detected in RG group, but it was not significant compared to placebo. On 50-m front crawl at maximal speed, no statistically significant intra- or inter-group differences were detected. Regarding secondary outcomes, no difference was demonstrated between preperformance and post-performance lactic acid levels. Comparing the treatment with placebo across follow-up, mean mid-arm muscle circumference (MAC) increased weekly and significantly by 0.23 cm (p=0.026), as well as 0.36% for gynoid fat (p=0.005). In addition, a decrease of 0.13kg in fat-free mass (p=0.067) was also detected. No statistically significant intra- or inter-group differences were detected for secondary outcomes. Conclusion: This pilot study provided early evidence that RG supplementation may positively affect nutritional status and partially, the performance of moderately trained swimmers. Further research is needed to clarify the mechanisms of action, the optimal timing of supplementation, as well as the most effective dose.