This paper, as part of broader research, explores how Sustainability Intelligence (SI) is transforming denim supply chain design through two case studies of internationally renowned Turkish companies: a Denim Exporter and a Denim Mill. SI is a framework developed to integrate environmental, social, and economic sustainability into complex industrial systems through SI Navigation (SIN) and SI Synthesis (SIS). The denim industry faces increasing pressure to address these sustainability dimensions while maintaining financial viability, yet systematic approaches to achieving these goals remain challenging. This research presents an in-depth analysis of sustainable practices implemented by two Turkish companies, focusing on their innovations in production techniques, responsible resource management, and commitment to social responsibility. The study critically examines how these companies adopt fashion sustainability across environmental, social, and economic dimensions while navigating constraints and opportunities in scaling sustainable solutions. The methodology for this paper draws on semi-structured interviews and thematic analysis, applied specifically to the two case studies of Turkish companies. The SI framework was developed through a broader research methodology employing grounded theory, including semi-structured interviews, focus group discussions, and multiple case studies, analysed using the constant comparative method. This ensures a robust and systemic understanding of sustainability in the denim supply chain. The paper highlights Supplying Intelligence as a driver of sustainable transformation. By applying Sustainability Intelligence (SI) framework’s key elements, the study demonstrates how denim manufacturers can align operations with sustainability goals, providing actionable strategies for achieving systemic change within the industry.