Purpose Online-to-offline (O2O) knowledge-sharing economy platforms have emerged as a new public channel for matching up knowledge providers with knowledge seekers. It can facilitate offline provision and consumption of high-quality tacit knowledge around a topic upon online search and payment (called offline knowledge service transaction). However, limited research investigated this new knowledge-sharing phenomenon in the field of knowledge management (KM). The purpose of this paper is to enrich KM literature by developing a theoretical model to explore determinants of offline knowledge service transactions via O2O knowledge-sharing economy platforms from both quality and price perspectives. Design/methodology/approach The model was tested with objective data crawled from Zaihang – a leading O2O knowledge-sharing economy platform in China. Findings The results show that, in the context of O2O knowledge-sharing economy, transactions of an offline knowledge service are positively related to its provider’s popularity, but negatively related to the price. Moreover, knowledge seekers are more likely to accept and purchase a high-priced service of a knowledge topic with a higher overall review score and supplied by a provider with lower popularity and shorter response time. However, the length of offline knowledge service has no significant association with its transactions. Originality/value This study contributes to KM literature through investigating a new phenomenon of tacit knowledge sharing (including provision and consumption) in the context of O2O service and the sharing economy. The results give implications for knowledge providers and platform managers to facilitate online transactions of offline knowledge services.