<p>This study investigates the relationship between indoor temperature and depressive symptoms among middle-aged and older adults in rural China. The data are from two waves of the China Health and Retirement Longitudinal Study (CHARLS). Indoor temperature was recored as hot, moderate, or cold. Mixed linear models (MLM) were employed to first analyze the cross-sectional association between indoor temperature and depressive symptoms in 2015, and then to examine the longitudinal relationship between indoor temperature transition and depressive symptoms over a four-year follow-up period. The MLM analysis revealed no significant association between hot or cold indoor temperatures and depressive symptoms. However, over the four-year follow-up, 12% of homes transitioned from moderate or cold to hot, and 2.6% from moderate or hot to cold. Notably, a shift from moderate or cold to hot was significantly associated with an increase in depressive symptoms, whereas a shift to cold was not. The results indicate that rising indoor temperatures in rural settings are linked to increased depressive symptoms among middle-aged and older adults. Maintaining a comfortable indoor temperature, such as through the installation of air conditioning, may help reduce the risk of depressive symptoms in this population and lessen the associated public health burden in China.</p>