BACKGROUND/OBJECTIVES: This study aimed to determine the impact of the daily consumption of kefir on the gut microbiome, body composition, and athletic performance of professional female soccer players. METHODS: The participants encompassed 21 females aged 18-29 years who were assigned to one of the two groups: the experimental group, which comprised females who consumed 200 mL of kefir daily for 28 days, and the control group, which comprised females who continued with their normal diet. Anthropometric measurements, dietary intake, the composition of the gut microbiome through 16S rRNA gene sequencing, and an athletic performance test known as the 30-15 Intermittent Fitness Test were performed before and after the intervention. RESULTS: The results of this study revealed that the consumption of kefir increased the microbial diversity (Shannon and Chao1 indices), wherein a significant increase was noted in the abundance of CONCLUSIONS: This study indicated that kefir consumption can positively affect the gut microbiota, which could in turn affect the athletes' performance. Therefore, to determine the effects of kefir as a functional food in sports nutrition over a longer period, more research should be conducted.