The aim of this study is to explore the relationships among sustainable purchase intention, environmental knowledge, social influence, and consumer evangelism, providing empirical evidence which validates the proposed hypotheses concerning these drivers’ functions as they mould actions by consumers within sustainability situations. The study does use a quantitative technique for the purpose of investigating the relationships among all of the variables of interest. It uses established theoretical frameworks including the theory of planned behaviour and social influence theory. The study confirms multiple hypotheses through statistical analysis because it highlights the importance of sustainable purchase intention, environmental knowledge, together with social influence in fostering consumer evangelism. Consumer evangelism is significantly impacted by sustainable purchasing intention, according to the study, and this relationship is strengthened by higher levels of environmental knowledge. Because social influence is what controls the impact that the sustainable purchase intention has on customer evangelism, advocacy actions are reinforced within favourable social environments. Environmental knowledge, furthermore, mediates the relationship between sustainable purchase intention and consumer evangelism, which indicates knowledge translates intention into action. This research contributes to the already existing literature by showing how sustainable purchase intention, environmental knowledge, and social influence all connect with and do promote consumer evangelism. Organizations do need to go about implementing educational initiatives in conjunction with marketing strategies which will lead to a group of aware and active customers. Future research avenues are proposed, including the exploration of demographic differences and the impact of digital platforms on consumer advocacy for sustainable practices.