The audit report fulfills the role of reducing information asymmetry between agent and principal. The structure of disclosure of information produced by these intermediaries has changed over time. In Brazil, as of 2016, the Key Audit Matters (KAM's) section was introduced in the structure of the audit report. Studies report that among the matters most reported by auditors are provisions and contingent liabilities. Thus, this study aimed to characterize the environmental factors that influenced independent auditors in the disclosure of KAM's related to environmental issues in environmentally sensitive Brazilian companies. To achieve this objective, a descriptive and documentary research was carried out, using content analysis as a technique. The documents analyzed were the Audit Reports and Explanatory Notes of Brazilian companies listed on the Stock Exchange Brasil, Bolsa e Balcão [B]³ and considered environmentally sensitive, according to the National Environmental Policy (PNMA). The paper results indicate that the provisions and contingent liabilities recognized and disclosed because of the companies' operating activities are not material. On the other hand, the lack of attribution of value to the contingencies disclosed may influence the independent auditors' assessment of the materiality of these obligations. Provisions and contingencies related to environmental accidents and asset retirement obligation are indirectly related and are determining factors for the disclosure of KAM's in the audit report.