Drawing on the Theory of Planned Behavior, the Technology Acceptance Model, Innovation Diffusion Theory, and Trust-Based Relationship Marketing Theory, this study develops an integrated framework to examine the relationships among social media marketing, perceived usefulness, perceived ease of use, social influence, personal innovativeness, brand trust, and purchase intention. Data were collected from 384 active social media users in Beijing, China, and analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM). The results indicate that social media marketing and its associated technological, social, and individual antecedents are positively associated with brand trust and purchase intention, highlighting the important mediating role of brand trust in shaping consumer purchase decisions. This study contributes to the social commerce literature by integrating multiple theoretical perspectives into a unified framework for explaining consumer purchase intention and provides practical insights for organizations seeking to strengthen consumer trust through effective social media marketing strategies.