Although e-commerce is evolving at an incredible speed, asymmetric information and opportunism have increased online purchasing risks and market inefficiencies. The lack of face-to-face contact and the inability of the customer to touch and feel tangible products necessitate that online business must provide customers with reliable information and convince customers of their trustworthiness. While the research on Third-Party Assurance Seals (TPAS) is not new, the effectiveness of TPAS has not been persuasively addressed by empirical studies. Our study is different from previous efforts in that it is comprehensive because it combines consumer trust, perceived risk, and influences of TPAS in the B2C e-commerce context. The results of the study show that (1) the effects of TPAS on perceived risk are channeled through perceived trustworthiness, thus demonstrating the mediating role of perceived trustworthiness in B2C e-commerce, (2) perceived risk, perceived usefulness of website, and subjective norm appear to be significant predictors of intention to purchase from the website, (3) a third-party assurance seal strongly affects online shoppers' perceived trustworthiness toward online retailers, while the seal appears to have little effect on perceived risk directly; perceived risk is strongly associated with intention to purchase from the website.