The paper aims to assess the effectiveness of social media advertising on brand awareness, interest, desire, and action (AIDA) among Gen Y and Gen Z consumers in Malaysia. Ego involvement and brand popularity were introduced into the AIDA model to reflect consumers' behaviour in modern advertising. An online questionnaire was deployed, where a total of 435 (229 Gen Y and 206 Gen Z) usable samples were collected and analysed using AMOS-SEM. Social media advertising is effective in creating brand awareness and brand interest. However, the effect on brand desire and brand action was only significant on Gen Zs. Ego involvement positively moderates the relationship between brand awareness and brand interest. However, brand popularity only mediates brand awareness and brand action among Gen Y consumers. The findings suggest the need for marketers to craft different social media advertising and brand popularity strategies at different levels of brand AIDA.