<p>Construction of tunnels is highly prone to cost overruns and schedule delays due to inherent geological uncertainties in subsurface conditions. These uncertainties, combined with information asymmetry, promote opportunistic behavior among stakeholders and undermine project performance. This study investigates the influence of subsurface uncertainty and information asymmetry on the behavior of contracting parties through an empirical analysis of three real tunnel construction projects. The objective is to evaluate whether observed behaviors align with those theoretically predicted by economic models, specifically principal–agent (P–A) theory. A qualitative analysis is conducted to assess how deviations between actual subsurface conditions and design estimates influence stakeholder behavior. The findings indicate that the employer (principal) adopts conservative risk transfer strategies in response to inadequate site investigations, prompting the contractor (agent) to pursue profit-maximizing behavior. The assessment demonstrates that the empirical behaviors observed across the projects are consistent with theoretical predictions derived from P–A theory. This study is among the first to provide empirical evidence illustrating how subsurface uncertainty and information asymmetry generate strategic, incentive-driven behaviors in tunnel construction projects. The findings provide a foundation for developing improved contractual frameworks and monitoring strategies aimed at enhancing project performance in tunnel construction.</p>