Determining the value contribution of IS investments is a crucial task to support conscious decisions, e.g. about the scope or for or against the implementation of these investments. IS investments transform an enterprise not only in its IS related architecture, but often enable enhancements within the business related architecture. Valuating IS investments from an integral point of view therefore means to measure the value contribution to all affected artifacts of an enterprise. Enterprise architecture (EA) used as a coordinative framework to valuate enterprise transformation may help to support this goal. We propose a valuation approach for IS investments based on EA offering two advantages: As through EA all artifacts of and their relationships within an enterprise are known, the impact of IS investments on all architectural layers can be identified and attributed to the IS investments as an integral value. Furthermore EA provides (detailed) models of all artifacts changed. These models can be used to support the valuation of the IS investments? impact on all affected artifacts. To demonstrate how this valuation approach can be tailored for valuating a concrete IS investment, we apply it to the exemplary case of valuating an IS investment enabling the on demand integration of service providers. Therefore we model the enabled enhancements of this IS investment on the business and business process architecture, relating on the basic optimization problem of capacity planning within a certain business process. A case study of the payment transaction process of a banking transactions provider finally shows the applicability of the valuation approach.