BACKGROUND: Chronic hepatitis B (CHB) treatment adherence has been poorly studied worldwide. We evaluated long term virological and adherence outcomes to antiviral treatment in CHB patients. METHODS: A prospective 183 Brazilian CHB patients cohort treated with monotherapy or combination adefovir dipivoxil, entecavir, lamivudine and / or tenofovir disoproxil fumarate was studied in a reference tertiary center. Treatment adherence was evaluated by a validated questionnaire named "Assessment of Adherence to Antiviral Therapy Questionnaire" (CEAT-HBV) within three year-periods (2010/2011, 2013/2014 and 2014/2015). RESULTS: CEAT-HBV identified 43% (79/183) patients with non-adherence to antiviral treatment and among them, 67% (53/79) were viral load positive. The main causes associated with non-response to antiviral treatment were drug resistance variants followed by non-adherence, insufficient treatment duration and other causes. Single-dose pharmacokinetics demonstrated 35% (23/65) antiviral non-adherence. Two years after the first assessment, the CEAT-HBV indicated that 71% (101/143) subjects adhered to treatment (per-protocol population). However, 21% (40/183) of the patients could not be evaluated and were excluded. The main reasons for exclusion were death (20/183), 11 out 20 deaths due to hepatocellular carcinoma. Hepatitis B virus (HBV) booklet was used for medical education. The third CEAT-HBV assessment (2014/2015) showed that 83% (112/135) patients were compliant with treatment adherence (per-protocol population). Long-term evaluation showed that adherence rate based on CEAT-HBV continue to increase after 4-years (p<0.001). CONCLUSIONS: The results highlight the importance of CHB therapy adherence assessment monitoring. Long-term adherence outcomes were dynamic and it is possible to increase the migration rate to adherence/HBV DNA negative group.