Objective: The present study aimed to explain the role of social capital in the ESG (Environmental, Social, and Governance) maturity of Iranian professional sports clubs.

Methodology: This research was conducted using a qualitative approach and the Glaserian Grounded Theory method. Data were collected through semi-structured interviews with 20 experts (including sports management specialists, professional club managers, and experts in corporate social responsibility and sustainable development) who were selected via purposive and theoretical sampling until theoretical saturation was reached. Data analysis was performed in three stages: open, selective, and theoretical coding. The reliability of the coding was confirmed using the test-retest method (89%) and intra-subject agreement (88%).

Findings: The data analysis yielded 52 initial codes categorized into four main categories structural, relational, and cognitive social capital, and the challenges and requirements of ESG maturity with “social capital as a driver of ESG maturity in professional sports clubs” emerging as the core category. The findings indicate that communication networks, mutual trust, and shared values enhance clubs’ operational capacity to implement sustainability policies.

Discussion and Conclusion: The results indicate that the three dimensions of social capital serve as the pivotal mechanism for ESG maturity in clubs; however, transitioning to the desired state of sustainability depends on addressing structural challenges such as weak governance, lack of reporting systems, insufficient strategic prioritization, and establishing the necessary institutional and cultural prerequisites within the country’s professional sports sector.