The literature suggests that the success of an information system among others depends on its utilization. In this paper, we argue that operational IT business alignment is an important driver of system usage and thereby of the market success of the supported business process. Using an embedded case study in four branches, the back office, and the IT department of a retail bank, many findings of the recent alignment literature can be supported. Using a strict business process perspective, we also offer new insights by showing that alignment is important for IS success in operations as well and positively influences post-implementation IS usage. In particular, mutual understanding between the units and shared domain knowledge not only between IT and business but also between different business units supported by the same core IS turned out to be very important factors of IS usage that have so far been neglected.