Using a sample of non-financial firms listed on the Shanghai and Shenzhen A-shares in China from 2012 to 2022, this paper empirically examines the effect of the internal compensation gap among executives on firms’ environmental protection investment, and further investigates the moderating role of equity concentration in it. The study finds a significant positive correlation between the internal compensation gap among executives and corporate environmental investment, i.e., increasing the pay gap will promote the level of the firm’s environmental investment. While equity concentration will weaken the positive effect of the executive internal compensation gap on corporate environmental investment. The findings of the study will enrich the research on executive internal compensation gap and corporate environmental investment, and offer new ideas for enterprises to improve the incentive mechanism of executive compensation and promote corporate social responsibility.