Based on the analysis of the 2012 Sustainability Reports from four companies of different segments (Telecommunications, Insurance, Cosmetics and Mining), this research sought to understand the prevailing rationality in this type of publication, in relation to the concepts of instrumental rationality and substantive rationality, based on Guerreiro Ramos. To accomplish this goal, the theoretical framework presented a discussion about the concepts of social responsibility, sustainability, substantive rationality, instrumental rationality, organizational identity and corporate reputation. Regarding the methodological procedures, collected documents were studied using content analysis, which allowed the creation of categories of observation, which are: (1) Relationship with Stakeholders; (2) Institutional statements and frameworks; (3) Legal Aspects, and (4) Triple Bottom Line balance. Next, each category was related to a set of characteristic elements of the two rationales listed, creating two different classifications. According to the results, in general, it was possible to identify the predominance of elements related to instrumental rationality in most speeches, which confirms the initial assumption and indicates the utilitarian calculation largely seen in these documents. As a practical matter, this study’s findings contribute to the management of organizations, once it becomes possible for these companies to ponder over and problematize their positioning and their actions in relation to sustainability, observing if the option for a more superficial discourse that seeks only a good corporate image is as effective as a discourse that reports organizational values and practices that address the real challenges of a current sustainable management. In addition, these findings may raise new questions about the subject – such as how the evolution of speech in sustainability reports of the one company over time would be, which could be better explored by further studies.