This study is the first to test the impact of knowledge sharing on life satisfaction. Based on social exchange theory, social capital theory, and self-determination theory, we tested a mediation pathway through which knowledge sharing affects life satisfaction via its influence on perceived quality of relationships with colleagues. Drawing on social role theory, we also examined the moderating role of gender on the relation between colleague relationship and life satisfaction. While social capital theory and self-determination theory suggest that quality colleague relationships have a positive impact on life satisfaction, social role theory suggests that the strength of this relationship varies on the basis of gender. Data collected from 246 full-time workers supported the mediation path, even when job satisfaction was controlled. While gender moderated the effect of colleague relationships on life satisfaction, the moderated mediation effect of knowledge sharing on life satisfaction was not supported. Our results suggest that knowledge sharing, as an important work behavior, not only promotes effective work-related outcomes but also has a positive impact on individuals’ subjective well-being. Theoretical implications are discussed.