Archaeological sites are fragile, non-renewable heritage environments where visitors’ inappropriate behavior may cause irreversible damage. This study designed and evaluated a VR serious game, Guarding the Terracotta Warriors, to promote visitors’ responsible visiting behavior intention at archaeological sites. Examining the Terracotta Warriors Museum as a case study, this study identified conservation needs through literature and case analysis, expert interviews, and preliminary visitor interviews, and translated them into four design requirements: path guidance for visiting boundaries, reflection on visiting order, contextualized risk decisions, and concrete feedback on behavioral consequences. Based on the MDA framework, these requirements were further transformed into interactive game mechanisms. A within-subject experiment with 46 participants compared the VR serious game with conservation-content-matched video instruction, followed by semi-structured interviews with 20 participants. Quantitative results showed that the VR serious game produced significantly higher scores than video instruction in presence, experience satisfaction, conservation-related attitude, awareness of consequences, personal norms, and responsible visiting behavior intention. Task load was slightly higher in the VR condition, but its mean score remained below the midpoint of the seven-point scale, indicating a relatively modest level of perceived task load. Qualitative findings further indicated that embodied exploration, safe-to-fail risk decisions, visitor-order feedback, and irreversible restoration feedback helped participants understand conservation boundaries and behavioral consequences. This study provides a design framework and empirical evidence for using VR serious games to support responsible visitor education at archaeological sites.