Agile is now a mainstream approach used by developer teams at software organizations. However, many of these organizations still employ traditional governance methods, negatively impacting agile team performance, quality and morale. To address this issue, we applied the Design Science Research Framework to develop Agile governance guidelines by harmonizing CMMI V2.0 and SAFe 5.0. Specifically, we matched CMMI V2.0 governance practices to SAFe 5.0 roles, practices and artefacts. The resulting guidelines were validated, first by means of a survey and then through interviews with process improvement practitioners and agile experts who worked on a fictitious case study. The survey participants, especially those more familiar with SAFe practices, stated that the proposed harmonization was meaningful. Agile experts participating in the case study confirmed that the proposed guidelines were practical and comprehensive, as well as consistent and complete. Pending further empirical validation, these guidelines constitute a crucial step towards Agile governance.