Technological innovation can improve the resource efficiency and accelerate the transformation of energy production mode, which offers attractive opportunities for low-carbon development of traditional energy firms. However, whether technological innovation can generate a better environmental result for traditional energy firms remains to be explored. This paper develops a panel regression model to examine the effect of technological innovation on environmental performance of energy firms based on the data of 136 energy firms in China from 2009 to 2019. The results indicate that, first, technological innovation has significantly improved energy firms’ environmental performance, increasing environmental strengths by 0.056% and decreasing carbon emissions intensity by 0.015%. Second, these effects are weaker for energy firms with more government subsidies, providing new evidence for the removal of fossil energy subsidies. Finally, negative media coverage also significantly weakened the boosting effects of technological innovation on environmental performance, revealing a “dark side” of media coverage on environmental management of energy firms. These findings have practical implications for managers and government agencies to improve environmental performance of energy firms.