Lack of trust has been identified as a major obstacle to the adoption of online shopping. However, there is paucity of research that investigates the effectiveness of various trust building mechanisms, especially the interactions amongst these mechanisms. In this study, three trust building mechanisms (i.e., third-party certification, reputation, and return policy) were examined. Scenario survey method was used for data collection. 463 usable questionnaires were collected from respondents with diverse backgrounds. Regression results show that all three trust building mechanisms have significant positive effects on trust in the online vendor. Their effects are not simple ones; the different trust building mechanisms interact with one another to produce an overall effect on the level of trust. These results have both theoretical and practical implications.