Objective To explore the association between type 2 diabetes mellitus (T2DM) and hepatitis B virus-related hepatocellular carcinoma (HCC). Methods Research data were derived from a follow-up database of hepatitis B virus infection established by the Affiliated Xinyu Hospital of Nanchang University in 2010. The patients without baseline HCC were grouped into diabetic group or non-diabetic group according to whether or not they had T2DM. Cox proportional hazard regression model was used to analyze the association between T2DM and hepatitis B virus-related HCC. Results Of the 435 patients who were followed up for 2 245.89 years, 68 were new cases of HCC. The incidence density of HCC was 30.28 per thousand person-years. Sixty-four patients with T2DM were assigned to the diabetic group, and the other 371 patients were assigned to non-diabetic group. The follow-up time was 331.27 years and 1 914.62 years in the diabetic and non-diabetic groups, respectively, and the incidence densities of HCC were 51.32 per thousand person-years and 26.64 per thousand person-years, respectively; and the difference of the incidence densities was significant (χ²=6.80, P<0.05). After adjusting for age, career, smoking and drinking, Cox regression analysis showed that the risk of HCC in the T2DM patients with hepatitis B virus infection was 2.13 times that in the non-diabetic patients (95% confidence interval[CI] 1.18-3.87). Conclusion In this cohort, T2DM is associated with hepatitis B virus-related HCC, and T2DM increases the risk of HCC in hepatitis B virus infected patients.