The green and digital transitions are reshaping vocational education and training (VET), driving growing demand for sustainability-related knowledge and skills. Research conducted in Bulgaria, Italy, Romania, and Türkiye shows that VET educators acknowledge this need; however, their capacity to implement advanced sustainability frameworks remains limited. Objectives: The paper presents an approach to integrating sustainability education into VET systems, developed in the framework of the international project GreenTeach. Methods/Approach: As part of the project, a secondary integrative analysis is conducted using two complementary evidence sets: baseline research involving VET educators and experts, and subsequent transnational piloting in four countries. Objectives: Quantitative descriptive results were triangulated with qualitative feedback and country-level implementation observations. Based on the collected evidence, a model encompassing a seven-stage integration cycle is suggested, including diagnostic baseline, strategic alignment, educator capacity building, curriculum translation, supported delivery, practice and partnership, and quality assurance with institutionalisation. Conclusions: The proposed model provides a practical context for VET providers to move from policy commitment to consistent implementation while allowing flexibility to adapt to different contexts.