Based on transaction cost theory and social exchange theory, using data from online buyers, this study not only empirically examined the effects of three governance mechanisms on perceived opportunism, but also explored the moderating roles of perceived uncertainty. The results from Hierarchical Linear Regression analysis showed that the reputation mechanism has a significant negative effect on perceived opportunism. Perceived uncertainty of shopping website’s behavior has moderating effect on the relationship between communication mechanism and perceived opportunism. Perceived uncertainty of product has moderating effects on the relationship between monitoring mechanism, reputation mechanism, communication mechanism and perceived opportunism.