How can assurance mechanisms be effectively enacted to promote users’ behavioral outcomes in online healthcare mutual aid platforms? To answer this research question, this study draws upon institutional trust theory and develops a research model to examine the influence mechanisms of two specific structural assurances (i.e., policy assurance and technology assurance) on users’ intentions and actual usage behaviors in a blockchain-enabled online healthcare mutual aid platform. We conduct a field survey in two time periods and employ structural equation modeling to test the research model. We find that both policy assurance that reflects institutional (i.e., legal, contractual, and regulatory) structures and blockchain-enabled technology assurance that describes reliable technical features (i.e., high data anonymity, immutability, transparency, and disintermediation) play salient roles in facilitating users’ trust in platform, which in turn affects their behavioral intentions and actual usage behaviors in the online health mutual aid platform. The research findings provide a comprehensive understanding of how platform assurances influence users’ behavioral outcomes in the evolving context of blockchain-enabled applications.