<jats:p>The almost absence of sustainability reports in Portugal prepared using the Global Reporting Initiative (GRI) guidelines in public sector (PS) entities led to the study of the strategic responses to institutional pressures, as suggested by Oliver (1991), in the few entities that publish such reports. The objective of this chapter is to determine the institutional factors that motivated sustainability disclosure in GRI reports. An interpretative approach through open questionnaire was used to analyze the strategic responses to the institutional pressures and expectations provided by PS entities. The results show that not all the institutional factors that lead Portuguese PS entities to disclose their social responsibility are in the acquiescence line, accommodating other strategic responses. Thus, this acquiescence is verified when the consistency with organizational goals is high and when the constraints and the multiplicity of stakeholders are low. </jats:p>