This book constitutes the refereed proceedings of two long-running events held along with the CAiSE conference and related to the areas of enterprise, business-process and information systems modeling: - the 26th International Conference on Business Process Modeling, Development and Support, BPMDS 2025 and - the 30th International Conference on Exploring Modeling Methods for Systems Analysis and Development, EMMSAD 2025. The conferences were taking place in Vienna, Austria, during June 16-17, 2025. For BPMDS 12 full papers were carefully reviewed and selected for publication from a total of 39 submissions. The BPMDS papers deal with a broad range of theoretical and applications-based research in business process modeling, development and support. For EMMSAD 13 full papers and 3 short papers were accepted from a total of 37 submissions after thorough reviews. EMMSAD focusses on modeling methods for systems analysis and development.