The Global Reporting Initiative (GRI) guidelines have emerged as an important instrument used by firms to structure the content of sustainability reporting (SR). This development has led to the question of whether the elaboration of GRI SR is beneficial to a firm’s financial performance. In this study, building on signaling theory, we carry out an empirical investigation of the impact of GRI SR on firm profitability and the factors moderating that impact. Drawing from the China Stock Market and Accounting Research (CSMAR), the WIND Economic, and the Chinese Research Data Services Platform (CNRDS) databases, we identified a sample of 122 listed firms with GRI SR in China. We then employed an event study method to compare the firms following GRI SR with a set of matched firms reporting sustainability without following the GRI guidelines. The results show that GRI SR significantly increases firm profitability. Moreover, firms with local political ties reap more benefits from GRI SR, while the moderating effect of central political ties is not significant. Surprisingly, the performance impact of GRI SR is negatively correlated to the firm’s internationalization level.