Fuzzy Logic has traditionally found an application in control theory, systems analysis, and artificial intelligence [9] [7]. However, it is very difficult to apply it to traditional software engineering. There is evidence that fuzzy logic can help in avoiding early assignment errors in SW engineering methods [1]. The authors have developed a technique that allows object oriented business process modeling. In this paper they propose a fuzzy logic extension to the method. Fuzzy sets can depict the uncertainty on the cost driver. Thus cost driver uncertainties have less impact on the model. The approach is new since it applies fuzzy logic to process modeling, and not to control or expert systems.