This research examines how firms' environmental, social and governance (ESG) performance impacts their capacity utilisation using data from listed firms in China from 2009 to 2022. We find that firms' ESG performance significantly elevates their capacity utilisation with an inverted U-shaped relationship. All three dimensions of ESG-environmental performance, social responsibility and governance-positively affect capacity utilisation, addressing gaps in enhancing firms' capacity utilisation through ESG practices. We identify an indirect transmission channel through which firms' ESG practices influence capacity utilisation, marking a pioneering discovery in our study. Using structural equation modelling (SEM), we confirm that firms' ESG practices enhance capacity utilisation by improving competitiveness and customer stickiness. Additionally, we discuss potential heterogeneity in the impact of ESG performance on capacity utilisation, considering factors such as ownership structure, industry, financial constraints and equity arrangements. Our findings provide insights for governments and companies aiming to incorporate ESG principles into their decision-making processes to enhance capacity utilisation.