<p>The association among body mass index (BMI), sleep traits, and depressive symptoms remains unclear, particularly among reproductive-age adults who play a significant role in society. This study explored the associations of BMI, sleep traits, and depression in reproductive-age adults, and the mediation of sleep traits on the association of BMI and depression. Based on the National Health and Nutrition Examination Survey (NHANES) 2013–2020, reproductive-age adults aged 18–49 were included. The associations among reproductive-age adults’ BMI, sleep traits, and depression were analyzed by the generalized linear models. Mediation analyses were used to examine whether sleep traits mediated the association of the reproductive-age adults’ BMI with depressive symptoms. A total of 2,586 participants were enrolled. The prevalence of the depression symptoms was 24.0%. Adjusted generalized linear models showed BMI was positively related with depressive symptoms score, snoring frequency and trouble sleeping, while negatively associated with sleep duration in reproductive-age adults. Snoring frequency, sleep time, wake time, and trouble sleeping were positively associated with depressive symptoms score. Mediation analyses revealed a mediating effect of snoring and trouble sleeping in the association between BMI and depression, accounting for 28.0% and 34.4% of mediating associations, respectively. After gender stratification, snoring frequency and trouble sleeping, as mediators, explained 24.7% and 19.9%, respectively, of the association of BMI with depression in females. In conclusion, BMI was positively associated with depression in reproductive-age adults. Mediating effects of snoring and trouble sleeping in the association of BMI with depression.</p>