We present a new approach for assessing the business performance of a mobile user interface (UI) project at its predevelopment stage. Traditionally, the performance measurement of a mobile UI is made from the perspective of usability. Yet, as the number of mobile phone users is rapidly increasing, and, given that stakeholders are beginning to realize the importance of the UI, there is a growing demand to measure its business performance quantitatively as well as qualitatively. This article presents a model that can facilitate Return on Investment (ROI) estimations pertaining to the development of a mobile UI before the service with the new UI is launched. We base our method on stated preference data for the purpose of applying a conjoint analysis. Subsequently, we evaluate the viability of the proposed model quantitatively by comparing the estimated ROI at the predevelopment stage with the actual sales revenue achieved after the launch of the service. The proposed model was successfully applied to real‐world mobile UI design projects at Korea Telecom. Its benefits are demonstrated here through a case study. © 2012 Wiley Periodicals, Inc.