This chapter examines the integration of Environmental, Social, and Governance (ESG) dimensions into Small and Medium-sized Enterprises (SMEs) business models. Zaman et al. (2025) highlighted that sustainability remains a multifaceted and evolving paradigm within economics and business. Small and medium-sized enterprises (SMEs) are crucial to the global economy, serving as essential threads in its fabric by driving innovation, creating jobs, and fostering resilience. Micro-enterprises alone represent between 70% and 90% of all firms in OECD countries (OECD, 2017), while SMEs contribute approximately 60% of total employment and value-added across these economies (OECD, 2017). To integrate ESG criteria into business models, SMEs must depart from the traditional emphasis on financial performance alone. This requires an expanded conception of value creation that prioritizes environmental, social, and human capital stewardship and regeneration. This transition may involve either reconfiguring existing business models or designing entirely new sustainability-oriented frameworks. The chapter is structured into two main sections. The first provides a literature review, synthesizing theoretical perspectives and empirical findings on the drivers, constraints, and strategic implications of ESG integration in SME contexts. It discusses resource limitations, regulatory asymmetries, and the lack of standardized ESG tools tailored to smaller firms. The second section presents a comparative analysis of three enterprises from the Autonomie & Solidarité portfolio (Bon Spot, CRESMAR, and IoT), illustrating diverse pathways of ESG integration. Through these case studies, the chapter highlights the operational challenges and the transformative potential of sustainability-aligned business models for SMEs.