There is growing interest in the potential of grassroots innovations for the transition towards more just and sustainable societies. Nevertheless, there is lack of clear normative discussion regarding these processes. The paper strives to propose and test a framework that enables an analysis of how and in which sense specific grassroots innovation processes may be contributing to the construction of more just societies. To this end, we connect elements of the multi-level perspective on sociotechnical transitions (frequently used in the analysis of grassroots innovations) with elements of the capability approach, which offers a multi-dimensional perspective to justice. The framework is used to address two purposively selected empirical cases in two key sectors in Spain: an energy cooperative and a food purchasing group. We draw on the information of 25 individual interviews with members of these two cases, on observation, and on secondary sources. Information was processed by means of a qualitative content analysis. We draw on predefined categories from the framework, which was refined during the analysis. The paper illustrates that grassroots innovations may be contributing to justice in several aspects: they expand capabilities in different dimensions, improve public reasoning processes, and create better structural conditions for human flourishing. Nevertheless, these processes are not free of tensions and contradictions.