ABSTRACT: This study aims to investigate the impact of social media advertising on purchase intention by analysing the mediating role of consumer brand engagement (CBE). From the literature review, there are two issues that gain more attention from current marketing researchers because there are remaining differences in factors, concepts, definitions, or measurement dimensions. First, different factors are used as advertising elements in the context of social media. Second, CBE uses different concepts, definitions, and measurement dimensions. The study deployed an exploratory sequential mixed-methods design. Data collected from a sample of 560 Thai people engaged with social media advertising, as Thailand is the leading country in using social media in Southeast Asia, were analysed using structural equation modelling (SEM). The findings suggest that social media advertising consisting of credibility, informativeness, entertainment, and information access affects CBE (measured as a second-order construct) and purchase intention. Additionally, CBE affects brand loyalty and purchase intention. In addition, it is found that CBE fully mediates the relationship between social media advertising and purchase intention.