Conspiracy beliefs have negative effects on decision making in several life areas including health, ethical, political and environmental domains. But their influence on financial decisions is not known. The current study examines the mediational role of social trust in the relationship between non-financial conspiracy beliefs and stock market participation. First, exploratory findings provide preliminary cross-country evidence that conspiracy beliefs are associated with lower stock market participation. Next, three studies from close to 53,000 United States respondents show that conspiracy beliefs predict 8%-20% decrease in the odds of investing in stocks even after adjusting for several determinants of stock ownership including income, life satisfaction, cognitive ability and economic attitudes. Mediation analyses shows that conspiracy beliefs predict lower social trust, which in turn predicts lower stock ownership. Overall, the findings imply that endorsing misleading non-financial beliefs about the causes of socio-cultural events may potential impede financial decision making.