Trust is a major issue in e-markets. It is an even more prominent issue when online shoppers trade with small, less-established e-vendors. Empirical studies on Web seals show that small e-vendors could promote consumers’ trust and increase Web sales by displaying Web seals of approval. This article takes a theoretical approach to examine online trading when seals are used in e-markets. We establish an online shopper’s decision-making model to reveal the online shopper’s decision-making criteria. Criteria include when to trade with a well-established e-vendor and when to trade with a small, less-established e-vendor, with or without a Web seal. Based on our analysis of the research results, we reveal the price effect, the seal effect, the reputation effect, and their impact on a shopper’s decision-making process. Meanwhile, a social welfare analysis is conducted to further demonstrate the positive impact of Web seals on small, less-established e-vendors.