Abstract Background Vitamin D is essential for maintaining optimal bone health. The prevalence of vitamin D inadequacy in athletes is currently unclear. Objective The objective of this study is to determine the prevalence of vitamin D inadequacy in athletes. Methods We conducted a systematic review and metaanalysis. Multiple databases were searched and studies assessing serum 25-hydroxyvitamin D [25(OH)D] status in athletes were identified. Serum 25(OH)D is measured to clinically determine vitamin D status. Reviewers independently selected the eligible articles, assessed the methodological quality, and extracted data. Disagreements were resolved by consensus. Weighted proportions of vitamin D inadequacy [serum 25(OH)D \32 ng/mL] were calculated (DerSimonian–Laird random-effects model) and compared using Chi-squared (v2 ) test. Subgroup analyses were conducted and risk ratios (RRs) with 95 % confidence intervals (CIs) were reported.