This study illuminates factors driving skincare brand choice by examining the role of product effectiveness in the social media marketing context. Using quantitative approach with Structural Equation Modeling on data from 217 Gen Z respondents, the research focuses on two key social media marketing stimuli: nano influencer marketing and short video content marketing. The findings reveal that product effectiveness significantly mediates the relationship between these marketing stimuli and consumer brand selection. While various marketing stimuli can attract consumer attention, the perceived effectiveness of the product is the primary driver of brand choice. Additionally, the study highlights the importance of selecting influencers who share similarities with target audience and those who create genuine content to enhance perceived source homophily and perceived content authenticity. The implications for skincare brands suggest a focus on strengthening product effectiveness as well as promoting authentic, performance-based content and carefully choosing relatable influencers for stronger consumer choice.