Technology extra-role behavior (TERB) is critical for the success of online communities (OCs). However, the factors that determine individual TERB vary in different contexts. In addition, less attention has been paid to smoking cessation online health communities (OHCs). This study aims to explore what motivates users’ TERB in smoking cessation OHCs from a social support perspective. In this study social support (including informational, emotional, and esteem support) motivates individuals’ knowledge contribution and recommendation behavior, which are studied as two different TERB in smoking cessation OHCs. We tested the research model by analyzing 173 valid answers of an online survey from two smoking cessation OHCs. The results show that emotional support positively affects knowledge contribution, and esteem support has a positive impact on recommendation. Informational support exerts influences on emotional and esteem support. The findings extend our understanding on the determinants of TERB in the context of smoking cessation OHCs, and offer practical implications for the administration of smoking cessation OHCs.