A utopia of sustainable development is becoming established on the international stage. To get there, varied and complementary strategies must come into play—among them education. This trend is turning to the “Social and Solidarity Economy” (SSE), especially since the approval by the United Nations (UN) of the 2030 Agenda; the fulfilment of which demands adult education strategies and programs in line with the principles and values of sustainability. This article offers a response to that demand. It aims to carry out a reflective analysis that reveals the similarities between the principles and values of the SSE and those guiding the UN’s 2030 Agenda, with its 17 Sustainable Development Goals (SDGs). Based on the results of this analysis, we will argue that training in the competencies for sustainability, essential in achieving the SDGs, is among the main functions of education within the SSE framework. Further, in order to make educational programs more sustainable, such training must be included in their operating objectives. The work uses a hermeneutic methodology based on the existing literature and gives particular attention to UNESCO’s directives on training in key competencies for sustainability. The significant contribution the results make is to show: (a) the emphases of each approach and their similarities; (b) how the two are complementary; and (c) the potential, and need, for creating synergies based on their respective strengths. A further original contribution is a proposed basic guide for the design of training activities geared towards gaining the normative competency that UNESCO has identified as key to sustainability. This innovative proposal will be useful for improving the quality of adult training programs, thereby contributing to the achievement of the SDGs in communities.