Purpose: The purpose of this study is to investigate the effects of intrinsic and extrinsic motivation on knowledge sharing and the moderating effects of individual demographics, organizational context and cultural context in that relationship. Design/methodology/approach: This study conducted a meta-analysis of 44 studies involving 14,023 participants to examine the direct and moderating effects of motivation on knowledge sharing. Findings: Results revealed that both extrinsic and intrinsic motivational factors were associated with higher levels of knowledge sharing, while the effect was stronger for intrinsic motivation. Moreover, results revealed that substantial variance was explained by moderating variables. Further investigation revealed that individual characteristics (age, gender), organizational context (organizational setting vs. open system, IT infrastructure) and cultural context (collectivism, uncertainty avoidance, performance orientation, power distance) moderated the motivation and knowledge sharing relationship. Research limitations/implications: As a meta-analysis, this study is confined to variables that have been frequently analyzed in prior research. Future research could further increase our understanding of different types of knowledge sharing and various boundary conditions. Practical implications: Organizations should provide customized incentive systems to specific target groups to align motivation and knowledge sharing. Multinational organizations may consider different motivation schemes across countries to better suit cultural differences. Originality/value: Despite a growing number of studies highlighting the important role of motivation in predicting knowledge sharing, the evidence is mixed. Based on a meta-analysis, this study identified true relationships and identified moderating effects that help explain prior mixed results.