In the digital era, social media plays a pivotal role in transforming sports fan culture. The present study aimed to investigate the role of social media in shaping fan culture in Iranian sports and to develop a paradigmatic model for this phenomenon. This qualitative research employed the grounded theory approach (Strauss and Corbin). Data were collected through semi-structured interviews with 19 experts in media and sports (6 females and 13 males), using purposive and snowball sampling until theoretical saturation was achieved. Data analysis was conducted using MAXQDA software and involved open coding (187 initial codes), axial coding (93 concepts), and selective coding (23 core categories). The central phenomenon identified was “Digital Fan Culture Formation.” This phenomenon is influenced by causal conditions (Strengthening Digital Fan Identity, motivational and emotional content, the role of unofficial fans, humorous content, and emerging interactive technologies), contextual conditions (globalization and cultural diversity in fandom, digital culture-building and value creation, fan information and education, features of popular platforms in Iran, differences among fan groups, and digital fan economy), and intervening conditions (negative impacts and challenges of social media, strategies for managing content challenges, team marketing and branding, infrastructural and legal limitations, as well as cultural and traditional constraints and values). The main strategies include shaping fan behaviors, enhancing fan motivation and spirit, and fostering fan interactions and communications. Consequences are divided into positive (increased fan loyalty and participation, social and cultural cohesion, team economic development, improved fan behaviors) and negative (increased inter-fan conflicts). The findings indicate that social media elevates fan culture from physical limitations to a global, inclusive, and dynamic space; however, challenges such as ethnic biases, filtering, and negative content require strategic management. This model can serve as a foundation for media policymaking and sports management in Iran, emphasizing the strengthening of digital infrastructure and educational content.