This article analyzes through a case study how Social Marketing practices are structured by sustainable designer fashion brands and how they influence product acquisition in digital environments. The study is grounded in discussions on sustainable consumption and the role of digital platforms in shaping purchasing behavior. The research is qualitative and descriptive, combining bibliographic research with a case study approach of Four Fingers, a sustainable designer fashion brand located in Florianopolis, Brazil. Findings indicate that the integration of Social Marketing and Digital Marketing practices can significantly influence the acquisition of sustainable designer fashion products online. Key strategies include maintaining a consistent digital presence to foster engagement and strengthen brand community; creating shared experiences, such as the Traveling Skirt (Saia Viajante) initiative, which promotes personalization, belonging, and emotional connection; transparent communication about materials and production processes; and the production of authentic, educational content reinforcing sustainability and authorship values.