Despite the increasing demand for sustainable development among Certified Public Accountant firms due to the more severe competitive environment, there is a dearth of research on a sustainability performance evaluation model for these firms' managerial decision-making. Therefore, by utilizing a multiple criteria decision-making model based on the Balanced Scorecard and combining Decision Making Trial and Evaluation Laboratory with Analytic Network Process and modified VlseKriterijumska Optimizacija I Kompromisno Resenje methods, this study sets up a model that can clarify the mutually influential relationships and comment weights of evaluation criteria, which have so far been ignored in prior studies on Certified Public Accountan firms' performances and the current situation of their sustainability performance. Based on interviews with partners of Taiwanese Certified Public Accountant firms, this paper finds that Client is the most important factor, followed by Internal processes, Learning and growth, and then Finance. The empirical result shows that client orientation rather than price-cutting may be a right strategy. In addition, more efforts are needed to improve Taiwanese Certified Public Accountant firms' sustainability performance. The results provide Certified Public Accountant firms’ decision-makers with a managerial reference for building sustainability performance evaluation systems and for seeking out the priorities in sustainability performance strategies. [ABSTRACT FROM AUTHOR]