The Fourth International Workshop on Process Querying (PQ 2019) aims to provide a high-quality forum for researchers and practitioners to exchange research findings and ideas on methods and practices in the area of process analysis, management, and querying. Process querying studies (automated) methods, techniques, and tools for managing, e.g., filtering, inquiring, manipulating, or updating, models that describe observed and/or envisioned processes, and relationships between the processes with the ultimate goal of converting process-related information into decision-making capabilities.