Circular economy (CE) is a model that is gaining significance in the context of sustainable development and environmental protection, focusing on minimizing waste generation and maximizing the use of available resources through recycling and extending product life cycles. The implementation of CE in various European Union countries demonstrates diverse approaches to resource management, waste production, and energy efficiency improvement. These differences primarily stem from varying strategies, national policies, levels of social awareness, and technological advancements. The article identifies the key challenges and barriers associated with CE implementation in selected countries—Poland, the Netherlands, and Romania—and highlights specific areas requiring improvement and adaptation. It emphasizes the critical role of aligning national policies with the EU guidelines, promoting ecological education, and investing in innovative technologies and solutions that support sustainable development. Additionally, it points to the need for developing appropriate waste management infrastructure and encouraging businesses and consumers to change habits and engage in pro-environmental actions.