Background <p>The association between dietary protein intake and liver cancer risk has rarely been reported. The aim of this study was to explore whether the intake of dietary protein from various sources is differentially associated with liver cancer risk in the Chinese population.</p> Methods <p>This large-scale prospective cohort study collected diet information by validated food frequency questionnaires at baseline in two population-based cohorts in Shanghai, China. Dietary protein intake was calculated using the China Food Composition Table. Cox proportional hazards regression models were utilized to estimate the hazard ratio and 95% confidence interval.</p> Results <p>A total of 60,915 men and 72,655 women were included in the analysis. By the end of 2020, 594 men and 335 women had been identified as incident cases of liver cancer during median follow-up time of 15.28 years and 20.01 years, respectively. In both men and women, total protein intake and major dietary protein sources showed null associations with the risk of liver cancer in categorical analysis based on quartiles, continuous analysis with increments per standard deviation, and trend analysis.</p> Conclusions <p>There was no evidence of a prospective association between total protein intake or any of the major dietary protein sources explored and the risk of liver cancer. Further validation through other large-scale cohort studies is needed in the future.</p>