The present paper focuses on the environmental pillar of a new and innovative framework for sustainability assessment of VET - Vocational Education and Training - providers. By employing case study methods on a research sample of 6 VET providers in the Mures County, Romania, we have determined the sustainable development challenges that VET providers face. The results are used to elaborate the core subjects of the framework in accordance with existing practices at VET providers. The framework is established based on the 3 pillars of sustainable development: environmental, social and economic, embedded in the 7 social responsibility core subjects referenced in ISO 26000: organizational governance, human rights, labor practices, the environment, fair operating practices, consumer issues, community involvement and development. A new layout is developed for the evaluation of the 30 framework indicators on couple values (indicator accomplishment – indicator significance), ranked from 0 to 5 for each of the two categories. The paper also presents a methodological approach in 4 stages and 13 steps that applies to the assessment process. It facilitates the representation of results in the sustainability assessment chart and diagram, which are exemplified for the environmental area performance indicators. Validation of the methodology in action is performed on a case study of a VET provider, the Chamber of Commerce and Industry Mures in Romania, demonstrating the consistency of the method in what concerns the results from the environmental pillar.