The socio-labour integration of people with disabilities is a major social problem for European countries and, especially, for Spain. Sheltered workshops, with their productive activity, are a kind of Work Integration Social Enterprise (WISE) whose aim is to create jobs for those people, supporting them through an insertion process into the labour market. Given the need to publicize the important role of sheltered workshops, the aim of this study is to contribute to the academic debate by measuring the added value of this kind of social enterprise and to provide empirical evidence of their social and economic impact. To do so, the impact of a specific sheltered workshop, UNEI, located in the Spanish region of Andalusia, is analyzed. Results allow us to conclude that, firstly, there is a demand to measure the impact caused by sheltered workshops and social enterprises in general, and that SROI methodology is the most appropriate methodology. And, secondly, being based on results of this method and on a sensitivity analysis application, sheltered workshops contribute to sustainable development, generating an impact much higher than could be expected, surpassing the economic and personal limits of the people involved and benefitting society as a whole.