The purpose of this study is to investigate, evaluate and provide empirical evidence regarding the role of environmental performance in moderating the effect of carbon emission disclosure and financial performance on firm value in basic materials sector companies listed on Indonesia Stock Exchange during the 2021–2024 period. This research is based on the inconsistency of previous findings regarding the effect of carbon emissions disclosure and financial performance on firm value, as well as the unclear role of environmental performance as a moderating variable in explaining the effect between carbon emissions disclosure and financial performance. This study employs a quantitative approach, using secondary data obtained from bloomberg terminal, companies' annual and sustainability reports, and the official website of the Ministry of Environment and Forestry (KLHK). The analytical method employed is Moderated Regression Analysis (MRA) to test the research hypotheses. The independent variables in this study are carbon emission disclosure and financial performance, the dependent variable is firm value, and environmental performance serves as the moderating variable. The study’s findings demonstrate that carbon emission disclosure and financial performance have a significant positive and direct influence on firm value. However, environmental performance is not able to moderate the effect of carbon emissions diclosure on firm value. In contrast, environmental performance is proven to moderate the effect of financial performance on firm value. Thus, carbon emission disclosure and financial performance are play more important as a sign of environmental responsibility and as a way for investors to evaluate a company’s sustainability and prospects.