Universities can make a significant contribution to sustainability, and the development of sustainability competences in their graduates should be a key outcome of their courses. We propose an assessment framework for enabling and evaluating the attainment of sustainability competences in University students. We outline its six steps, offering tools on how to assess the alignment of University programs’ Learning Outcomes (LOs) to sustainability and how translate them into competences for sustainability. We provide approaches to evaluate existing assessment methods in terms of enabling students to develop and apply their competences, guidance on how to conduct the assessments to collect data on student performance and eventually how to use the data, and evidence collected to evaluate if the students are developing the intended competences. We illustrate the application of the assessment tool in a University case study and we draw conclusions on the evidence it offers to how higher education practitioners can benefit from its use.