•Individual group joining behavior positively affects individual online demand and reputation.•The higher person-group fit, the better individual online demand and reputation in online health communities.•Physicians’ title negatively moderates the relationship between individual group joining behavior and their online demand. Group service in online health communities (OHCs) is a novel form of service where physicians can share knowledge and collaborate with others to provide better services to patients through the Internet. Although many literatures have explored the impact of individual group joining behavior on group performance, few researches have been done on the relationship between individual group joining behavior and their personal performance. To fill this gap, we examine the effect of individual group joining behavior on their online demand and reputation using a unique panel dataset of 8,069 physicians from a large online health community in China. In addition, how the effects differ among physicians with different clinic titles are explored and several robustness checks including propensity score matching analyses are conducted to control for self-selection among physicians. The results show that, physicians’ group joining behavior and the person-group fit will positively affect their online demand and reputation. Furthermore, we find that physicians’ clinic title has a negative moderating effect.