As the energy demands increasing globally, a lot of energy related challenges are evolving including global warming, energy sustainability and environmental pollution, which have forced countries to endorse renewable energy development policies proactively. As in result a lot of renewable energy projects are carried out around the world, which are facing numerous challenges and barriers, resulting in failure for many of recent projects. Although governments have launched several initiatives vis-à-vis renewable energy development in response, however such actions are limited to promote the renewable energy consumption, the implementation strategies for renewable energy projects and best practices are still overlooked. This study presents a systematical investigation on critical success factors (CSFs) affecting renewable energy projects. Through systematic process, a total of 41 significant success factors (SSFs) for renewable energy projects have been identified which are further extracted into 5 critical success factors (CSFs). In addition, CSFs have been prioritized through multiple linear regression analysis by SPSS 20, using the survey results of 272 firms working on renewable energy projects in Pakistan. Finally, a novel causal model is established to demonstrate the interaction mechanisms for ensuring success in renewable energy projects by the SSFs and CSFs. The results demonstrate that environmental factors are the predominant CSFs with highest correlation (0.592) which show the significant effect (33.8%) over project success. The findings not only help to understand the critical success factors for renewable energy projects in Pakistan, but also offer useful references for other countries that intend to promote renewable energy projects in the future.