Sustainable development and sustainability transitions are becoming increasingly significant in research and practice due to immense challenges that social, economic, and environmental ecosystems are grappling with, such as climate change. Projects as interventions are game-changers in addressing these challenges, as decisions made in projects impact both project success and sustainability transition trajectories in societies. This study developed a conceptual framework through which the cruciality of decisions in different scenarios is evaluated to showcase how the priority of project managers\\\' decisions at the project level (i.e., micro-level) not only impacts the same level but also has butterfly effects on overall sustainability transitions at the broader societal levels (i.e., meso-level and macro-level). To reflect real-world complexities, we drew on various perspectives and theories, namely projects-as-interventions perspective, project-as-practice perspective, socio-technical perspective, actor-network theory, and decision theory, along with comparative analysis. The findings underscored that the project managers\\\' awareness of sustainability transitions throughout the project life cycle (PLC) may change the prioritization and cruciality of decisions, and those can subsequently trigger societal sustainability transitions. Besides, the sensitivity of decision-making in line with sustainability in international and regional projects is more than in national and local projects. Therefore, this study primarily contributes to making sustainable decisions within projects while navigating sustainability transitions at the thebroader societal levels.

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