Hepatitis B infection is a global health issue. When considering patients with rheumatic diseases, this is no different. By using immunosuppressant drugs, such as DMARDs and biologics, viral reactivation is possible, leading to serious consequences on the patient. We report 3 cases of association between ankylosing spondylitis and hepatitis B with the use of immunosuppressant drugs. Case 1 was a patient with previous HBV infection using DMARD. Cases 2 and 3 were patients chronically infected by HBV during immunosuppressant therapy. The management of HBV infection during immunosuppressant therapy is challenging and needs multidisciplinary support.