Spread mooring systems are associated with high level uncertainties and risks during tanker loading/unloading operations. In addition, the design of such complex systems consists of many subjective and imprecise parameters. Therefore, in the present study, a fuzzy based decision support methodology is designed to overcome aforementioned characteristics. The fuzzy methodology incorporates qualitative and partially known information into the decision support model and provides a robust mathematical framework for modeling of the spread mooring systems. Proposed model is based on the analytic hierarchy method (AHP) and the technique for order performance by similarity to ideal solution (TOPSIS) methods in a fuzzy environment where the vagueness and subjectivity are handled with linguistic and fuzzy values. The fuzzy AHP method is used to analyze the structure of the mooring system selection problem and determine the weights of the attributes while fuzzy TOPSIS method is employed for ranking the spread mooring systems. The case study demonstrates the effectiveness and feasibility of the proposed methodology. (C) 2011 Elsevier Ltd. All rights reserved.