Success in electronic commerce relies greatly on customer's trust. While other studies have examined various factors affecting the online trust, a few have researched on the joint effects of perceived risk and website reputation on purchase intention using online trust as a mediator. The current study attempts to fill the gap. 300 samples of online shoppers participated in web-based questionnaires using a quota sampling technique. Based on the confirmatory factor analysis (CFA), the measurement is valid and reliable. Using the structural equation modeling (SEM) technique, we confirmed the significant direct effects of the perceived risk and the website reputation on the purchase intention. Furthermore, both factors did have the significant indirect effects on the intention through the online trust. In addition to extending theoretical insight into the online trust as a mediator for the effects of the perceived risk and the website reputation on the purchase intention, web-based vendors may adopt the findings to adjust their online stores to raise customer's trust and ultimately increase the possibility of the purchase.