Sustainable tourism performance of cruise ports is a critical determinant of the long-term competitiveness of both ports and destination regions. This study aims to develop and apply a novel picture fuzzy sets (PFSs)-based decision-support system to systematically evaluate cruise ports’ sustainable tourism performance by integrating qualitative expert judgments with quantitative operational data. The proposed framework adopts a multi-attribute group decision-making structure, in which PFSs are employed to explicitly capture uncertainty, hesitation, and neutrality in expert evaluations. Criteria weights are determined using an extended PFS-based weights by envelope and slope (WENSLO) method, while cruise port rankings are obtained through a PFS-integrated multi-attributive border approximation area comparison (MABAC) approach. The applicability of the proposed PFS–WENSLO–MABAC hybrid model is demonstrated through a case study of major cruise ports in T¨urkiye. The results indicate that the number of cruise passengers (0.5601) and the number of cruise ships (0.4218) are the most influential determinants of sustainable tourism performance, with Ku¸sadası Cruise Port (0.9029) achieving the highest overall ranking. Sensitivity and robustness analyses confirm the stability of the ranking outcomes under varying weighting scenarios. The findings provide actionable insights for port authorities and policymakers by identifying priority performance dimensions and offering a reliable analytical tool to support strategic planning and sustainability-oriented decision-making in cruise tourism.