This study investigates how the e-business platform certification system affects online trust-building mechanisms for existing brands. Integrating theories of online trust and brand knowledge, we propose that brand awareness and brand image, two sub-dimensions of brand knowledge, contribute to building brand trust in online stores. The effectiveness of e-business platform services also contributes to consumers’ trust in the online channel. Instead of regarding the platform guarantees as the antecedents of online trust, we hypothesize that the e-business platform certification system positively moderates the effects of building online trust. We test the research hypotheses using questionnaire data collected through an online survey and use structural equation modeling to analyze the data. The findings support our proposed model. The theoretical and managerial implications are identified based on the results.