The article examines the transformation of Ukraine’s energy sector during the war and outlines the role of green energy sources in the post-war reconstruction of the national energy system. Particular attention is paid to the structural changes in Ukraine’s energy balance and the development of renewable energy in the context of European energy transition trends. It is emphasized that despite significant potential for the expansion of solar, wind, biomass, and small hydropower, the share of green energy sources in Ukraine’s energy system remains lower than the European average. The impact of the full-scale Russian invasion on the functioning of Ukraine’s energy infrastructure is analyzed. Military actions have caused extensive damage to power generation facilities and transmission networks, disrupted supply chains, and reduced investment activity in the energy sector. Special attention is given to the destruction and temporary occupation of territories where a substantial share of renewable energy capacity had previously been concentrated, which has negatively affected electricity generation and slowed the implementation of new projects. The study identifies key institutional, financial, and regulatory challenges that constrain the development of green energy sources in Ukraine. Among the most significant barriers are instability in tariff policy, accumulated debts within the renewable energy support system, limited access to long-term investment resources, and insufficient development of modern energy storage systems and smart grid technologies. It is argued that overcoming these challenges requires comprehensive reforms in energy governance and the introduction of effective policy instruments to stimulate sustainable investment in the sector. The paper outlines strategic priorities for strengthening the role of green energy sources in the post-war reconstruction of Ukraine’s energy sector. These priorities include modernization of energy infrastructure, expansion of decentralized generation systems, development of energy storage technologies, strengthening international financial cooperation, and integration of Ukraine’s energy market with the European energy system. Alignment with EU energy and environmental standards and the implementation of decarbonization policies are also considered essential elements of Ukraine’s long-term energy transformation. It is concluded that the development of green energy sources can become a key driver of Ukraine’s energy system reconstruction, energy security, and sustainable economic development in the post-war period. The implementation of innovative technologies and strengthened cooperation with international partners will contribute to the formation of a modern, decentralized, and environmentally sustainable energy system.