Previous research has found a negative linkage between neighbourhood social participation and depressive symptoms in Western countries, but the cross-sectional design of these studies limits the ability to infer causality. Little attention has been paid to socio-psychological pathways linking neighbourhood social participation to depressive symptoms among older adults in China. This study aimed to examine the impact of neighbourhood social participation on depressive symptoms among older adults in China. It also further explored the mediating roles of physical activity, social contact among neighbours, and contact with own children in the relationship between social participation and depressive symptoms. Data obtained through three waves (2011, 2013, and 2015) of the China Health and Retirement Longitudinal Study were used. The sample consisted of 10,105 individuals aged 60 and above and 24,623 person-year records captured during these three waves. Depressive symptoms were assessed using the Center for Epidemiology Studies of Depression scale. Results showed that respondents' depression decreased with an increasing level of neighbourhood social participation, more time spent on physical activities, and a higher frequency of contact with neighbours and with own children. These factors were found to partly mediate the relationship between neighbourhood social participation and depression. The negative relationships between social contact and depression and contact with own children and depression were both strengthened by neighbourhood social participation. In conclusion, physical activity, social contact among neighbours and contact with own children are mechanisms through which neighbourhood social participation lowers the risk of depression among older adults in China.