In the era of digital marketing, social media influencers have emerged as powerful catalysts shaping consumer behaviour and brand perceptions. This study investigates the impact of Instagram influencers endorsed by Nike on consumer behaviour in India, focusing on brand perceptions, attitudes, purchase decisions, and brand loyalty. Through a mixed-methods approach combining quantitative surveys, qualitative interviews, and content analysis, data was collected from 150 participants representing diverse demographic segments. Key findings reveal that exposure to Instagram influencers positively influences consumer perceptions of Nike, leading to improvements in brand familiarity, image, trust, purchase intent, loyalty, and perceived quality. Participants exposed to influencers demonstrated higher purchase intentions and were more likely to consider and purchase Nike products compared to unexposed participants. Additionally, Nike's influencer marketing strategies significantly contributed to fostering brand loyalty, with influencer engagement, brand authenticity, customer satisfaction, and loyalty programs emerging as key predictors. Content analysis of influencer posts revealed predominant themes such as product features, lifestyle imagery, user testimonials, and promotional offers, highlighting the diverse strategies employed by influencers to engage their audience and promote Nike products. Sentiment analysis of participant comments indicated predominantly positive sentiment towards influencer content, underscoring its effectiveness in eliciting favorable reactions from consumers. This study contributes to the literature by advancing theoretical understanding, providing methodological insights, and offering practical implications for marketers. Recommendations for future research include exploring cross-cultural variations, conducting longitudinal studies, employing experimental designs, and addressing ethical considerations in influencer marketing practices. By embracing these recommendations, researchers can further enrich our understanding of influencer marketing dynamics and its implications for brands and consumers in the digital age. Keywords: Social media influencers, Instagram, Nike, consumer behavior, brand perceptions, purchase decisions, brand loyalty, influencer marketing.