This volume constitutes the proceedings of the 12th IFIP WG 8.1 Conference on the Practice of Enterprise Modeling held in November 2019 in Luxembourg, Luxembourg. The conference was created by the International Federation for Information Processing (IFIP) Working Group 8.1 to offer a forum for knowledge transfer and experience sharing between the academic and practitioner communities. The 15 full papers accepted were carefully reviewed and selected from 35 submissions. They are grouped by the following topics: modeling and ontologies; reference architectures and patterns; methods for architectures and models; and enterprise architecture for security, privacy and compliance.