This policy brief delves into the complex web of challenges plaguing Serbia’s energy sector, examining the combination of events during the winter of 2021-2022 that triggered the current crisis. A breakdown at the Nikola Tesla Thermal Power Plant, exacerbated by underinvestment and mismanagement, collided with the global energy crisis. The Russian invasion of Ukraine further heightened concerns, revealing the vulnerabilities of Serbia’s energy supply, which relies heavily on Russian-owned entities. These events forced Serbia into unprecedented expenditures to secure energy supplies and reopened questions about its strategic orientation and energy transition. This study scrutinises the role of Russian ownership in Serbia’s energy landscape, mainly focusing on NIS Oil Company, and extends the analysis to broader energy transition dynamics and geopolitics. It sheds light on the historical context of Russian investments in oil and gas, their impact on Serbia’s energy security, and the complex interplay between Russian, Chinese, and Western interests, local politics, and environmental considerations.