Social-Environmental Emancipation: for a Critical Environmental Theory tries to hermeneutically discuss the contrasts of social emancipation from the Marxist tradition of the Frankfurt School in its two versions, systematized by Theodor Adorno and Max Horkheimer - the first one taking root in the interdisciplinary materialism and the second one marked by the context of the instrumental reason -, and of the contemporary theoretical-critical ones such as Boaventura Souza Santos. Starting from the analytical-descriptive assessment, the subject is developed by presenting the status quo of social emancipation from the conceptualization of instrumental rationality as an effective paradigm of the capitalist system. Then, the influences of this rational modality are studied from the ethical-political assumptions that substantiate it, that is, Human Rights, the dignity of the human being and the hegemonic democratic models, in order to define the limits of social emancipation in the developmental-liberal scenario. Once the critical context of social emancipation through theoretical and critical contingencies has been structured, the environmental crisis from the capitalist production mode, based on the technical-scientific instrumentality, is unveiled so that the social environmentalism is discovered as a new interlocutor of the political action in what regards the social-environmental emancipation. On that purpose, the text dialectically projects itself in the emancipatory perspectives found in the social-environmental rationality, as opposed to the instrumental rationality, and uses the descriptive analysis of the environmental economicsbased co-optation tools to justify the fact that the current ecological crisis, parameterized by the capitalist scientificity and its derivatives – especially the inequality of the social actors, increasing poverty and environmental degradation - has consistent convergent points and politically demands new knowledge. The political action model in which the text is located is referred by ecosocialism, positioning political ecology as precursor of a new social and environmental culture based on the collectivist concept of the way of existing with the others - human and non-human.To conclude, the Critical Theory assumption is updated in what regards its principiologic dimension: the social-environmental emancipation as a possibility to understand the complexities of the present times and to be able to reinterpret and give a new meaning, from political, social and environmental matrixes, to the social-environmental rationality as an assumption for a configuration of the man-nature relationship.