This chapter explores the intersection of impact investing and public–private financing models (PPFMs) in advancing circular economy (CE) enterprises, with particular emphasis on SMEs. It highlights how SMEs, despite their pivotal role in resource efficiency and sustainable production, remain constrained by systemic barriers such as risk-averse lending, information asymmetries, and inadequate institutional support. The analysis demonstrates that blended finance, donor-backed guarantees, technical assistance, and enabling government interventions can lower investment risks, enhance investor confidence, and build SME capacity to adopt circular models. Drawing on case studies from Europe, Africa, and Asia, the chapter illustrates diverse financing mechanisms, including specialized credit facilities, PPPs, and innovation hubs, that successfully mobilize capital for circular enterprises. Despite these advances, challenges of scalability, policy coherence, and long-term sustainability persist. The chapter concludes with policy recommendations that call for institutionalized blended finance platforms, harmonized regulatory frameworks, expanded guarantee schemes, and stronger multi-stakeholder collaboration to accelerate circular SME development.