The fast-tracked growth of social media platforms has essentially changed the way cosmetics brands interact with consumers in the emerging markets. The present study investigates the impact of Social Media Marketing Activities (SMMAs) which include Entertainment, Interactivity, Trendiness, Customization and Electronic Word-of-Mouth (eWOM) on Brand Loyalty and Willingness to Pay a Premium Price with mediating influence of Brand Equity (Brand Awareness, Brand Image and Brand Trust) in the fast-growing cosmetics industry in India. Primary data were collected using a structured five-point Likert scale questionnaire employing a quantitative, cross-sectional survey design to gather primary data among 200 consumers of cosmetics across Hyderabad, Mumbai, Delhi, and Bengaluru. Hypothesis testing was done using Partial Least Squares Structural Equation Modelling (PLS-SEM). Findings have also indicated that all the five SMMA dimensions have a significant positive impact on Brand Equity ( 0.238–0.329, p < 0.001). Brand Equity, in turn, significantly predicts Brand Loyalty (β = 0.524, p < 0.001) and Willingness to Pay a Premium Price (β = 0.487, p < 0.001). Analysis by mediation proves that the relationship between SMMAs and both outcome variables is partially mediated by Brand Equity (indirect 0.176 -0.271). The model accounts 61.4% of the variance in Brand Loyalty and 57.8% in Willingness to Pay a Premium Price. These results highlight the strategic significance of purposeful social media use to cosmetics brands with Indian consumers and present actionable implications to brand managers, digital marketers and policymakers...