Background <p>The association between night sleep duration and depression has been documented in previous studies, but remains controversial. This study aims to explore the relationship between depression and nighttime sleep time in Chinese elderly people and its influencing factors.</p> Methods <p>The data originated from the China Health and Retirement Longitudinal Study 2020 (CHARLS 2020), including 8,365 residents aged at least 60. The logistic regression analysis model was used to analyze the depression-related factors, and the restricted cubic spline (RCS) was used to examine the dose-response relationship between night sleep duration and depression.</p> Results <p>In 2020, the prevalence of depression among the Chinese elderly was 41.02%. Females, living in rural areas, having no spouse/partner, receiving medical treatment within 1 month, experiencing physical pain, perceiving poor health status, and being dissatisfied with the relationship with children were risk factors for depression in the elderly. The relationship between night sleep duration and depression differs by gender. In males, shorter sleep (less than 6&#xa0;h) raises the risk of depression; in females, it shows a U-shaped relationship. The RCS indicated a non-linear dose-response (male χ² = 30.56, <i>P</i> &lt; 0.001; female χ² = 32.26, <i>P</i> &lt; 0.001). After stratification a non-linear relationship was still present (<i>P</i> &lt; 0.05).</p> Conclusion <p>The impact of night sleep duration on depression is different between male and female. For males, less than 6&#xa0;h of sleep is a risk factor, and more than 6&#xa0;h has no significance, while for females, a U-shape exists, with too little (less than 6&#xa0;h) or too much (9&#xa0;h or more) are both risk factors for depression.</p>