It is essential to understand the determinants of university students’ decisions to engage in sustainable energy behaviors, as this understanding has implications for the development of communication and education strategies to promote sustainable energy behaviors. The present study aims to investigate the impacts of affective and cognitive factors on sustainable energy behaviors among university students. It will explore the affective factors of self-responsibility and social norms and the cognitive factors of environmental concerns, perceived self-efficacy, perceived self-benefits, and action knowledge about sustainable energy behaviors. A simple random technique was used to select participants from undergraduate students at King Mongkut’s University of Technology Thonburi (KMUTT) in Bangkok, Thailand. Questionnaire surveys were completed by 426 participants in May and June 2020. Multiple regression analyses were used to test the ability of affective and cognitive variables to predict university students’ participation in sustainable energy behaviors. The results revealed that participation in sustainable energy behaviors was significantly impacted by the perceived benefit of sustainable energy behaviors, students’ concerns about climate change, perceived self-efficacy, and social norms; self-responsibility and action knowledge had no significant impact. These findings indicate that communication that focuses on climate change and approaches that enhance students’ self-efficacy and the perceived benefits of sustainable energy behaviors could help promote such behaviors among university students. The sustainable energy behaviors of other social groups, including students’ family members and colleagues and the general public, are also influential as they can motivate students to change their behavior.