Using A-share listed companies from 2014 to 2020 as samples, combined with the manually collected PPP project data, this paper empirically investigates the impact of listed companies’ participation in PPP projects on audit fees. The results show that compared with the non-participating companies, the audit fees of the companies participating in the PPP project increase significantly, and the deeper the participation (the more the number of PPP projects and the greater the capital contribution), the more the audit fees increase. By distinguishing the industry and geographical distribution of PPP projects, it is found that the above effects are more obvious when the location of PPP projects is inconsistent with the place of registration of the company and the industry of PPP projects is inconsistent with the company’s own industry. From the perspective of the PPP project return mechanism, user-paid and feasibility gap subsidy PPP projects have a more obvious impact on audit fees, and participation in government-paid PPP projects does not significantly increase audit fees. In addition, the participation of PPP projects will increase the auditor’s work input, and related companies are more likely to receive unqualified audit opinions. The above findings suggest that the participation of listed companies in PPP projects has a significant impact on auditor behavior decisions.