PurposeMegaprojects have a long-lasting impact on all three dimensions of sustainability-social, environmental and economic. The advent of the COVID-19 pandemic has further heightened the importance of sustainability due to its disastrous consequences on the global economy and business activities. This study aims to explore the interactions and interventions of various actors in the megaproject field to institutionalise sustainability.Design/methodology/approachThe current study adopted the organisational field approach as the theoretical lens to understand the decision-making process amongst multiple actors with conflicting interests that come together to play an active role in addressing a common interest of sustainability in megaprojects. A single case study has been undertaken using an Indian metro rail megaproject with multiple sources of data (interviews, documents, media reports).FindingsThis study showed that the institutionalisation of sustainability is dependent on interactions of various organisations and influences from institutions. Various institutional measures organised within the field to enhance sustainability practices before and during the COVID-19 pandemic are captured. Four institutional logics (instrumental, intrinsic, equivocal and political) that emerged from the case study are discussed. Finally, while not exhaustive, this study proposed recommendations that can help refine sustainability actions considering COVID-19 implications on megaprojects.Research limitations/implicationsThis study's findings emerged from a single case study. The developed conceptual framework can help further research with multiple cases of megaprojects in various fields or countries.Originality/valueThis study would be novel in advancing the organisational field approach in megaproject sustainability.