The thesis investigates why energy transition projects underperform relative to climate targets and how to manage their distinctive complexities. Building on a literature review and 18 semi-structured interviews with Fluor B.V. practitioners, it contrasts energy transition projects with conventional ones across six domains: people, technology, finances, resources, legal/regulatory, and project management methods. While some complexities are shared, energy transition projects face unique challenges, including a diverse client base with unclear objectives, lack of ownership for new technologies, heavy reliance on external funding and offtake agreements, a shortage of specialized resources, a dynamic multi-location regulatory landscape, and strong cross-sector interdependencies that create time-sensitive interrelations. The study also reveals a shifting management paradigm: away from traditional control-oriented approaches toward hands-off and combined styles, with greater emphasis on front-end development, proactive stakeholder engagement, and agile practices to cope with uncertainty and pace. To address these complexities, the research proposes a seven-step guiding checklist covering client and team integration, technology and financial feasibility, interface management among financial/legal/resources, regulatory compliance, resource planning, and tailored execution methods for energy transition projects. Practical recommendations include adopting agile management, concise meeting documentation, alliance-type contracting, stronger front-end design, and structured learning and cross-project knowledge sharing. Limitations include subjectivity and a small, niche sample (n=18) within project-based organizations; future work suggests broader datasets, improved contracting models, systematic knowledge capture, and long-term performance evaluations. Overall, the thesis contributes to energy transition project management by detailing specific complexities and offering actionable strategies and a practical checklist to accelerate project progression.