Online marketplace platforms finally arrived in Brazil, a business model that connects buyers with sellers through an intermediary party. This particularly application of commerce in large scale has brought with it several modifications in the relationship between companies and consumers, taking in account an online environment already quite loaded with uncertainties on buy process. However, large companies that act as intermediaries in these platforms, prioritize the volume of user accesses in their domains above the other activities related to the purchase process itself. The growing number of complaints and lawsuits seeking compensation for consumer losses indicates a decline in the industry as a whole. Considering that, this research seeks to investigate the relative importance of buyer perceptions on the reputations of third-party vendors and their effects on the perceived risk and trust relationship of the companies involved in the marketplace model and the consequent impacts on consumers online purchase intention. An online survey was conducted with Brazilian individuals who shopped at virtual stores over the last 12 months. The research s data confirmed all the hypotheses formulated, suggesting that evaluations of reputations of seller s influence in the intention to buy through perceptions of confidence and perceived risk. Some suggestions are proposed for companies in the e-commerce industry to optimize their efforts inside and outside marketplaces online.