Social media platforms have transformed from facilitating interpersonal communication into global commerce infrastructure. This review article analyzes the influence of social media marketing (SMM) on consumers’ buying behavior through scientometric assessment and critical thematic synthesis. Bibliometric mapping was conducted on a bibliographic dataset published between 2014 and 2025 to analyze annual scientific output, citation trajectories, leading authors and sources, productivity by country, keyword co-occurrence, collaboration networks, cocitation, bibliographic coupling, and thematic trends. The Findings reveal continued growth in publication output, with research emphasis shifting from broad topics such as social-media adoption and electronic word-of-mouth (eWOM) to SMM strategies including consumer engagement, influencer marketing, social commerce, personalization, short-form video, and emerging artificial intelligence (AI)-enabled practices. Critical synthesis found that SMM does not affect buying behavior through a singular direct effect. Instead, advertising, e-WOM, influencer marketing, user-generated content (UGC), reviews, engagement and social commerce exert influence through psychological processes such as awareness, trust, attitude, perceived value, engagement, and social influence. A proposed integrated framework illustrates how marketing stimuli contribute to psychological processes that determine purchase and post-purchase outcomes. These relationships are conditioned by moderators such as culture, demographics, product type, and platform features. Implications for an SMM-inspired research agenda are discussed, with particular attention to  purchase behavior, cross-platform comparison, artificial intelligence, privacy, and misinformation.