This study explores the impact of sustainable marketing on consumer behaviour and brand equity, using Simpli Namdhari’s—a 100% vegetarian omnichannel retailer in Karnataka—as a case study. As sustainability becomes a strategic imperative in retail, brands like Simpli Namdhari’s are leveraging ethical sourcing, residue-free produce, and community engagement to build trust and loyalty among consumers. The research employs a mixed-methods approach, combining surveys and interviews with 320 participants across Karnataka. Findings reveal that sustainability significantly enhances brand awareness, perceived quality, and emotional connection, leading to increased brand loyalty. Cultural alignment and digital engagement further amplify these effects. The study concludes with strategic recommendations for retailers aiming to integrate sustainability into their brand identity and marketing efforts.