Summary. Medication adherence is important for the success of nucleos(t)ide analogue (NUC) treatment for chronic hepatitis B. The aims of this study were to determine adherence to NUCs and factors associated with NUC adherence and to correlate NUC adherence with the occurrence of virological breakthroughs in patients with chronic hepatitis B. Consecutive patients with chronic hepatitis B receiving NUC were asked to complete a survey every 3 months. Adherence was also assessed by healthcare providers in the clinic. Adherence rate was defined as the per cent of days the patients took their hepatitis B virus medications during the last 30 days. A total of 111 patients were studied. The mean age was 47.7 years, 73.9% were men, 57.7% were Asian, 42.3% had postgraduate education and 80% had private insurance. Sixty-nine (74.1%) patients reported 100% adherence in the survey, while 78 (83.9%) reported 100% adherence to their healthcare providers. Patients with 100% adherence based on the survey were older (P = 0.02), more likely to be men (P = 0.006), and had higher annual household income (P = 0.04) than those with <100% adherence. In the 80 patients who completed three surveys, viral breakthrough was observed in 1/46 (2.2%) with 100% adherence on all three surveys, 1/18 (5.6%) with <100% adherence on one survey and 3/16 (18.8%) with <100% adherence on ≥2 surveys, (P = 0.06). In conclusion, adherence to NUC therapy in our patients with chronic hepatitis B was high but self-reporting of adherence to healthcare providers may be inflated. Patients with chronic hepatitis B with better adherence to NUC therapy had a trend towards a lower rate of viral breakthroughs.