Business Process Maturity Models (BPMMs) receive growing attention within digital transformation to evaluate the maturity level of business processes regarding specific capabilities. However, existing models are primarily descriptive, with limited prescriptive features and guidance to improve the current state. Besides, the assessment methods of popular BPMMs do not adequately reflect the indispensable role of information technology (IT), i.e., IT systems and information flow, for business process management (BPM) and process performance. Motivated by a research project with an industry partner, we apply the practice-oriented Action Design Research methodology to introduce our comprehensive and prescriptive “BPMMxIT” maturity model that integrates the IT and BPM perspectives. This study details the development and application procedures and provides generalised design principles to evaluate process performance and capability maturity for digital transformation. Transparency and reproducibility are facilitated by extensive supplementary material. Finally, theoretical implications and pivotal directions for organisational practice and further research are outlined.