Summary Background Patients with chronic hepatitis B (CHB) need long‐term antiviral treatment with nucleos(t)ide analogues (NA). Animal studies suggest that some NA may increase cancer risk, but human data are lacking. Aim To investigate cancer risks in patients with or without NA treatment. Methods We conducted a territory‐wide cohort study using the database from Hospital Authority in Hong Kong. The diagnosis of CHB and various malignancies was based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD‐9‐CM) diagnosis codes between 2000 and 2012. Patients exposed to any of the oral NA for CHB were included. The primary outcome was incident cancers. A 3‐year landmark analysis, with follow‐up up to 7 years, was used to evaluate the relative risk of cancers in treated and untreated patients. Results A total of 44 494 patients (39 712 untreated and 4782 treated) were included in the analysis. During 194 890 patient‐years of follow‐up, hepatocellular carcinoma developed in 402 (1.0%) untreated patients and 179 (3.7%) treated patients, while other cancers developed in 528 (1.3%) and 128 (2.7%) patients respectively. After propensity score weighting, treated patients had similar risks of all malignancies weighted hazard ratio (wHR): 1.01, 95% CI: 0.82–1.25, P = 0.899, lung/pleural cancers (wHR: 0.82, 95% CI: 0.52–1.31, P = 0.409) and urinary/renal malignancies (wHR: 1.04, 95% CI: 0.38–2.81, P = 0.944) when compared with untreated patients. Conclusions Oral nucleos(t)ide analogue treatment does not appear to increase cancer risk in patients with chronic hepatitis B. Given the beneficial effect on liver outcomes, our data support the current practice of long‐term anti‐viral therapy.