This review critically synthesizes and extends the influencer marketing literature by exploring how relational, psychological, and contextual mechanisms shape consumers' behavioral responses in digital environments. Adopting a multi-method research approach, Study 1 presents an extensive TCCM (Theory, Context, Characteristics, and Methodology)–guided systematic literature review of 172 articles to identify key theoretical foundations, empirical trends, methodological approaches, and research themes. Study 2 complements this with 18 in-depth interviews with academic experts and industry practitioners, offering deeper interpretive insights and contextual relevance of the findings. Together, these studies uncover central thematic drivers, including content and narrative strategies, psychological mechanisms, platform dynamics, and sponsorship disclosure. The findings imply that relational, narrative, and identity-based mechanisms have a greater influence on consumers' behavioral outcomes, including engagement behavior, psychological reaction, and symbolic alignment than rational and informational appeals. Therefore, this review advances the field by integrating affective, symbolic, and contextual variables into an overarching framework and suggests a future research agenda to address current theoretical and methodological deficiencies. The study offers a robust foundation for influencer marketing scholarship that is both contextually adaptable and psychologically grounded.