Adaptive reuse is a common approach for buildings that no longer serve their original function despite their good physical conditions. Such applications require the examination of the building regarding its qualities and capabilities. The focus of this study is the capability of the buildings to correspond to the user"s requirements following adaptive reuse processes, and the effects of new functions on the building performance optimization. Achieving reliable data in building performance evaluation will be possible only through the correct definition and association of the criteria. This study examines the adaptive reuse of Mugla Museum, a former prison building, through archive research, plan analysis, observations, and interviews. The result of the study has shown that the functional and perceptive performance of Mugla Museum is neutral, while the technical performance of the building has been found to be good. The building corresponds to its function with average performance, and the level of performance has the potential to be increased through adjustments in the building program or capacity increase. The study has shown that performance evaluation is necessary for determining the strengths and weaknesses of buildings. Within this context, developments in assessment methods would contribute to the betterment of adaptive reuse processes.