As QFD methodology is based on the voice of customers, it requires a group of individuals or decision makers (DMs) to express their preferences. However, there can be circumstances that DMs may not have a perfect knowledge of the problem to be solved; and it is inherent that every DM in evaluation group may not be able to give complete information. Thus it is necessary to involve incomplete preferences in the evaluation processes. The aim of this study is to improve the effectiveness of the evaluation process in QFD. The QFD methodology is extended by introducing a new group decision making (GDM) approach that takes into account incomplete information of DMs by means of fuzzy set theory. The proposed approach is applied in collaborative software development (CSD) process to demonstrate its potential.