Social media marketing has increasingly become a strategic channel for brands to engage and build relationships with consumers, particularly in trust-sensitive industries such as bio cosmetics. However, research on how Social Media Marketing Activities (SMMAs) shape consumer perceptions and behaviors in this sector remains limited. Guided by the Stimulus-Organism-Response (S-O-R) framework, this study examines how six dimensions of SMMAs, including informativeness, interactivity, personalization, trendiness, entertainment, and electronic word-of-mouth, affect consumer evaluations (perceived quality, value, and trust) and subsequent outcomes (satisfaction and purchase intention) in the bio-cosmetics market. A cross-sectional quantitative design was employed, and data were collected via an online survey from 342 Vietnamese consumers who actively use social media and have prior experience purchasing bio-cosmetic products. The proposed research model was evaluated using Partial Least Squares Structural Equation Modeling (PLS-SEM), which enabled the assessment of both measurement and structural relationships. The results supported all hypotheses, revealing that six dimensions of SMMAs, including informativeness, interactivity, personalization, trendiness, entertainment, and electronic word-of-mouth, positively shape consumer perceived quality, value, and trust, which subsequently enhance satisfaction and purchase intention. Among these factors, perceived trust emerged as the most critical driver, underscoring the central role of trust in building favorable attitudes and behavioral intentions toward bio-cosmetics brands. This study contributes to the literature by extending the understanding of how SMMAs operate in a niche but rapidly growing market and provides actionable insights for managers to design transparent, engaging, and trust-oriented social media strategies.
