The transition to a low-carbon energy future requires the mobilisation of private finance to accelerate the shift away from fossil fuels. While investment in green energy has surged, fossil fuel financing remains persistent, underscoring the need to understand the factors shaping investment decisions. Existing research has primarily examined retail investors' preferences for sustainable investments but has paid limited attention to professional investors' attitudes toward fossil fuel investments. This study addresses this gap by investigating the determinants influencing professional investors' decisions in the energy sector. Using a Multiple Discrete- Continuous Extreme Value (MDCEV) model—a method not previously applied in sustainable finance the analysis reveals that professional investors continue to exhibit a preference for brown firms. However, key factors such as professional roles, experience, and cognitive biases significantly impact their willingness to divest from fossil fuels. These findings highlight the complexities of sustainable investment decisions and underscore the need for targeted policies to steer capital toward green energy solutions.