Platform economies have reshaped competitive landscapes by embedding firms in networks of dense interdependence, in which value creation and capture depend on coordinated interactions among multiple actors. This theory-development article proposes a novel framework for understanding strategic complexity as an inherent structural property of digitally mediated markets. Strategic complexity arises from the interplay of multi-actor interdependence, shifting complementarities, coopetitive tensions, and platform-mediated governance mechanisms that simultaneously enable and constrain firm behavior. Traditional strategy theories, focused on dyadic relationships or internal resources, fail to capture the entanglement of business relationships in platform ecosystems, where coordination burdens, power asymmetries, and feedback loops amplify uncertainty and require continuous repositioning. Synthesizing insights from ecosystem, platform, and digital business literatures, the article develops six theoretical propositions that explain how interconnected relationships generate complexity and how firms can manage it through orchestration, selective governance, and adaptive positioning. By advancing a theory of digitally mediated strategic entanglement, this manuscript offers conceptual clarity for scholars and actionable guidance for managers navigating platform economies. Implications extend to ecosystem governance, competitive strategy, and the evolving nature of inter-firm dependence in digital markets.