Driven by the enactment of the Corporate Sustainability Reporting Directive (CSRD) and its integration of the double materiality concept, this paper examines the operationalization of this concept within a set of Portuguese-listed companies operating in high-pollution sectors, in anticipation of its mandatory implementation. The findings indicate that the early adoption of the double materiality concept was not widespread among the analysed companies. Companies behaved differently when faced with new disclosure requirements. Moreover, assessing material topics using this criterion is a multi-step and complex process involving multiple stakeholders. This may suggest that few companies value the benefits of early adoption, given the complexity of operationalizing the concept of double materiality.