Purpose: Researchers have shown great interest in the relationships among a toxic workplace environment, workplace stress, and project success, which have led to an expansive body of research on the topic. In light of this work, the current study explores the effects of a toxic workplace environment (TWE) and workplace stress (WS) as determinants of project success in the renewable energy projects of Pakistan. Based on the resource-based view (RBV) theory, the study proposes and tests a model with organizational support as a moderating variable. Research Methodology: A 30-item questionnaire survey was administered among staff of ten renewable energy project companies located in the vicinity of Karachi, Lahore, Islamabad (Pakistan). The target population was senior managers, middle-level managers, and administrative staff. Structural equation modelling was used to estimate the predictive power of the model. Results: A toxic workplace environment was found to have negative relationships with project success and workplace stress. Organizational support served as a moderator in the relationship between a toxic workplace environment and workplace stress and thus contributed to the success of a project. Conclusion: Toxic workplace environment and the resulting workplace stress have a negative effect on project success. Projects undertaken in the energy sector have tight deadlines, which create stress that leads to a range of mental and physical health problems. Workers facing these problems can ultimately suffer from such diseases as depression, anxiety, and insomnia. These issues lower morale and, thus, negatively affect productivity. The provision of organizational support can mitigate the negative effects.