Social media has become a primary environment for advertising communication, where traditional persuasion models are transformed into interactive and personalized forms. Influencer marketing combines personal branding, public visibility, and continuous communication with the audience, increasing perceived authenticity and reducing cognitive resistance. Theoretical mechanisms of social influence, such as normative, informational, and identification processes, explain its impact on followers’ attitudes and behavior. Empirical data show a moderate positive correlation between authenticity and trust (r = 0.42; N = 1,118), high reliability in measuring loyalty (α = 0.87; N = 808), and statistically significant effects from experiments with three and two groups (F = 5.42, p < 0.01; t = 3.21, p < 0.01). Qualitative interviews with 15 influencers provide additional context regarding trust-building strategies and parasocial relationships. The combination of quantitative and qualitative approaches confirms that influencers simultaneously affect cognitive, emotional, and social mechanisms, fostering identification and strengthening brand loyalty. Thus, influencer marketing is established as an effective tool for long-term digital communication and strategic brand positioning.