In the evolving landscape of digitally connected business ecosystems, traditional hierarchical structures are increasingly supplanted by platform-mediated markets where coordination emerges through decentralized mechanisms. This conceptual paper introduces the Platform Ecosystem Coordination Model (PECM), a novel framework that elucidates how strategic coordination is achieved without formal hierarchy. Drawing on organizational theory, strategic management, and information systems literature, the PECM delineates five core components: ecosystem orchestration hubs, relational governance protocols, algorithmic control interfaces, power diffusion channels, and dynamic adaptation loops. These elements collectively explain the redistribution of governance responsibilities, the deployment of non-hierarchical control mechanisms, and the balancing of power asymmetries among platform owners, complementors, and market participants. By integrating insights from platform governance and ecosystem interdependence, the framework highlights how digital technologies facilitate emergent coordination, mitigate opportunism, and foster value co-creation. Theoretical contributions include advancing understandings of non-hierarchical strategy in digital markets, while managerial implications offer guidance for platform leaders to optimize ecosystem health without centralized authority. The PECM provides a structured lens for analyzing power distribution in interconnected digital environments, addressing gaps in how coordination persists amid fluidity and interdependence. Future research directions are proposed to extend the model to emerging technologies like blockchain and AI-driven platforms.