Background: From the life course perspective, the childhood living environment exerts long-term effects on adulthood mental health. This study aims to examine childhood neighborhood quality, peer relationships, and trajectories of depressive symptoms among middle-aged and older Chinese adults using a large and representative set of survey data. Methods: The data were derived from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2018). Depressive symptoms were measured using the 10-item Center for Epidemiological Studies Depression Scale (CES-D-10). Childhood neighborhood quality and peer relationships were measured via a standardized questionnaire. Latent Growth Curve Model (LGCM) was used to study the trajectories of depressive symptoms according to different levels of childhood neighborhood quality and peer relationships. Results: The mean level of depressive symptoms increased first and then decreased in the follow-up period. Poorer childhood neighborhood quality and peer relationships were associated with higher levels of depression in adulthood (β=0.15 and β=0.29, p <0.001) at baseline and a faster increase in depressive symptoms with age for childhood neighborhood quality (β=0.10, p <0.05). Quadratic growth factors were generally not significant for both childhood neighborhood quality and peer relationships. Conclusions: Poorer childhood neighborhood quality are associated with a faster increase in the rate of change in depressive symptoms in later life. Efforts toward improving living conditions may help to prevent the detrimental health effects of such early-life disadvantages.