Background: This study aims to determine the factors affecting HBV DNA suppression in chronic hepatitis B patients with tenofovir disoproxil fumarate (TDF). Methods: A case-control was carried out from October 2021 to August 2022 on 182 chronic hepatitis B patients who had TDF therapy regularly for 24 weeks at H. Adam Malik and USU Hospitals in Medan, Indonesia. The history of the samples was obtained, followed by physical examination, and blood collection. CTLA-4 polymorphism examination was carried out using real-time PCR, while the serum CTLA-4 levels were assessed with ELISA. Results: The results showed that CTLA-4, HBV DNA, ALT, and CTLA-4 -1661G>A polymorphisms have a relationship with HBV DNA suppression in chronic hepatitis B patients with TDF. Conclusions: The levels of CTLA-4, HBV DNA, ALT, and CTLA-4 -1661G>A polymorphism have a potential relationship with the suppression of HBV DNA in chronic hepatitis B patients with TDF.