Tunnel projects frequently face variations, delays, and disputes that are difficult to settle with traditional project management techniques due to fragmented documentation and conflicting goals of contracting parties. The cost and time required for dispute handling necessitate advancements in management skills for efficient resolution. This study proposes a group support system (GSS), which incorporates the building information modeling (BIM) and Nash bargaining principles to facilitate data-driven, transparent, and fair dispute resolution. The BIM framework identifies the modified scope and predicts the potential outcome of variation claims from the actual project dataset, while the game theory finds the optimal settlement by balancing the employer’s and contractor’s payoffs to formalize the negotiation strategy. A case study on a variation dispute from a tunnel project demonstrates that the engineer rejected the claim at the first instance, and the contractor submitted an exaggerated claim for time extension. The proposed GSS predicted the dispute outcome based on construction dataset and utility functions of parties, demonstrating that it can enhance negotiation and dispute resolution efficiency for fair settlements. Finally, the research advocates for the digital transformation in the construction industry for claim management, negotiations, and dispute resolution to improve transparency, efficiency, and collaboration.