Whether and how multi-membership in online communities might relate to life satisfaction within the Chinese population remain unclear. This study adopts a gendered perspective to explore the mediating role of voluntary participation in the relationship mentioned above based on a cross-sectional analysis of 2558 respondents from the 2019 Chinese Social Survey (CSS). Multivariable regressions and a mediation analysis were adopted for analyses. The findings reveal that a higher level of multi-membership in online communities is associated with greater life satisfaction for both males (B = 0.31, SE = 0.11) and females (B = 0.10, SE = 0.02). Specifically, the positive relationship is partially mediated (6.6%) by increased voluntary participation among females, where involvement in multiple types of online communities correlates with a heightened likelihood of engaging in voluntary activities (B = 0.006, Z = 3.910), which in turn contributes to higher levels of life satisfaction (B = 0.114, Z = 2.760). However, voluntary participation does not exhibit a significant mediating role in the relationship between multi-membership and life satisfaction among males. These findings provide valuable insights into the intricate ways in which online interactions can affect voluntary participation and life satisfaction, underscoring the importance of considering gender differences in these dynamics.