The article analyzes the models and methods used to share methodologies in projects, programs, and project portfolios. Relevant literature sources are analyzed, including project management standards and the solutions they offer. Particular attention is paid to hybrid project management methodologies. Three stages of methodology hybridization are identified. The difference between syncretic methodology and hybrid methodology is determined. Three concepts of interaction between the project portfolio management system (the core of the syncretic methodology) and the project management system are considered. A data model (for the methodology interface) that generates a project for exchange with the portfolio management system is described. A model for classifying interfaces between methodologies of individual projects (or methodologies of individual parts of one project) within the project management system of a project-oriented organization (portfolio) is proposed. The following classification criteria are proposed: by the purpose of the interface, by the degree of forecasting future changes in the external and internal project environment, by the degree of use of artificial intelligence, by the degree of universality (applicability to other types of projects and project portfolios), by the methodology of the central management system, by the flexibility of configuration, by the degree of interface automation. The most commonly used types of interfaces between methodologies are characterized by four features. A model of data exchange through interfaces within the syncretic methodology is proposed. A SWOT analysis is conducted, strengths, weaknesses, opportunities that arise when applying the proposed interface models within the syncretic project management methodology, and threats that may arise are highlighted. Areas of further research in the selected direction are formulated: formalization of industry models of interfaces of the syncretic project management methodology at the level of the corporate methodology of a self-managed project-oriented organization (for infrastructure projects); formalization of industry methods for implementing interfaces between methodologies of individual projects and the syncretic core of the project portfolio management system within the syncretic methodology (for infrastructure projects); development of models for using artificial intelligence elements in interfaces between methodologies of individual projects within the project portfolio managed by the syncretic methodology; practical testing of models and methods of interfaces between methodologies of individual projects within the project portfolio, guided by a syncretic methodology in the implementation of projects (project portfolios) of infrastructure restoration in Ukraine by self-managed organizations. Conclusions from the conducted research are formulated.