<p>The use of the internet as a source of health information is widespread and growing rapidly. Despite a growing body of literature on online health information, little is known about the potentially negative psychological impacts of trust in such information. This paper examines the impact of trust in online health information on subjective well-being, utilizing data from the 2021 Chinese General Social Survey (CGSS). Our analysis reveals a negative correlation between trust in online health information and subjective well-being. To address potential endogeneity and ensure robustness, we employ instrumental variable estimation, propensity score matching regressions, and alternative specifications of the dependent variable. We identify multiple mechanisms through which trust in online health information influences subjective well-being: health behavior, health literacy, and health outcomes. Specifically, health behavior is measured by the intensiveness of online health information-searching behaviors. Health literacy includes the preference for traditional over modern medicine and well-being perception bias. Health outcomes are assessed through mental well-being. A high level of trust in online health information is associated with these factors, harming subjective well-being. Additionally, poor health status and lacking healthcare support exacerbate the negative impact. Our findings highlight the importance of improving health literacy and digital literacy to mitigate the adverse effects of spurious online health information on well-being. Heterogeneity analysis shows that the impact is more significant among individuals of low socioeconomic status or rural Hukou as well as those living in less-developed areas. This study contributes to our understanding of the complex role that trust plays in shaping well-being outcomes, offering insights that can inform public health strategies and policies.</p>