There are extensive empirical studies on online health communities (OHCs)—important platforms that help users manage their health conditions. However, little research has concentrated on the role of social support networks and user engagement. This paper aims to investigate the influence of social support networks on users’ health conditions via user engagement in health tasks, alongside the moderating effects of gender differences. We established a twoequation model using the data of 1,129 users in an OHC. The empirical results of our research model reveal that the size of a social support network, as well as individual activities and group member activities within the network, are positively associated with levels of user engagement in online health tasks. This paper also finds that the interactive relationship between three factors—(1) the association of social support network size and (2) individual user activities with (3) levels of user engagement—is complementary; further, it finds that the relationship between (1) social support network size, (2) group member activities, and (3) levels of user engagement is substitutable. Moreover, we observe that levels of user engagement in health tasks are positively related to users’ health conditions. In addition, our results show the moderating effects of gender differences on the relationship between social support, levels of user engagement in health tasks and user health conditions. The findings of this paper add value to the literature on OHCs and provide some insights into the management of OHCs for practitioners.