BackgroundFatigue is one of the most common and devastating Human Immuno-deficiency Virus (HIV) - related symptoms, with a varying prevalence in different study areas. In Ethiopia, there is a paucity of information on the magnitude and factors associated with fatigue among HIV/Acquired Immune Deficiency Syndrome (AIDS) patients. This may lead to under-diagnosis and eventually under-management of the symptom.MethodsInstitution based cross-sectional study design was conducted among 609 HIV/AIDS patients who were selected by using a systematic random sampling method. Data were collected by using interviewer administered structured questionnaire. Level of fatigue was measured by Fatigue Severity Scale.ResultsThe prevalence of fatigue was found to be 51.7%. The factors associated with fatigue were: Parity [AOR = 2.01; 95% CI: 1.09–3.71], CD4 count 200–499 cells/mm3 [AOR = 2.81; 95% CI: 1.58–4.99], anemia [AOR = 4.90 95% CI: 2.40–9.97], co-morbidities [AOR = 3.65; 95% CI: 1.71–7.78], depression [AOR = 3.68 95% CI: 1.99–6.79], not being physically active [AOR = 3.20 95% CI: 1.50–6.81], clinical stage II or IV HIV [AOR = 3.11; 95% CI: 1.51–6.40] and [AOR = 4.08; 95% CI: 1.37–12.14], respectively.ConclusionThe finding of this study revealed that fatigue is a common health problem among adult People Living with HIV (PLHIV). Factors associated with fatigue included: Parity, CD4 count 200–499 cells/mm3, Clinical Stage II or IV HIV, anemia, co-morbidities, depression, and not being physically active. The health care service needs to address the predisposing factors by provision integrated care including timely detection and treatment of comorbidities, mental health problems, and promote physical activity to slow down disease progression and then reduce exposure to fatigue.