Previous research in advertising reveals that consumers use a set of existing knowledge, including persuasion knowledge, topic knowledge, and agent knowledge, to form evaluations and responses to advertising messages (i.e., Friestad & Wright, 1994). Based on the persuasion knowledge model, schema congruity theory, regulatory focus theory, regulatory fit theory, and self-construal theory, this thesis investigates a framework of how consumers use these three types of knowledge to judge the credibility of green advertisements. This thesis then seeks to further explain why and how consumers in various cultures perceive different levels of credibility when they are exposed to the same green products’ advertisements. Two online experiments conducted in Vietnam and one in-person experiment conducted in both Vietnam and New Zealand demonstrate that in order to form evaluations of green message credibility, consumers recall both persuasion knowledge and topic knowledge. They use more persuasion knowledge when their cognitive resources are unconstrained than when their cognitive resources are constrained, and if they use a higher level of persuasion knowledge to process information and think that the advertisement is effective, they will have a higher perception of message credibility. Consumers use topic knowledge in the same manner, regardless of whether their cognitive resources are constrained or unconstrained. To evaluate brand credibility, consumers recall brand knowledge, and they use more brand knowledge when their cognitive resources are constrained than when their cognitive resources are unconstrained. Findings also reveal that consumers will perceive a higher level of message effectiveness and message credibility when the advertised message is framed in accordance with consumers’ chronic regulatory orientation. This is the case regardless of whether consumers are from an independent culture, where most people have a stronger promotion-focused orientation, or from an interdependent culture, where most people have a stronger prevention-focused orientation. The findings of this thesis expand the literature on the persuasion knowledge model and the evaluation of credibility in the context of green advertising. The findings document the positive effects of the use of persuasion knowledge on green message credibility, which is often overlooked in previous research. The studies contained in this thesis incorporate three types of knowledge in a framework and reveal when consumers use one type of knowledge more than others to evaluate green advertisement credibility. Ultimately, the comparative approach between cultures further allows for generalization of effects observed in an Eastern context to extend to global consumers and allows for clear sets of implications to be articulated about how green brands can achieve perceptions of message effectiveness.