Background: Highly Active Antiretroviral Therapy is efficacious in suppression of Human Immunodeficiency Virus (HIV) however, it is associated with numerous toxicities hence great effort has been put into development of antiretrovirals with better tolerability. The World Health Organization recommended dolutegravir as first-line antiretroviral therapy however, recent studies have raised concerns regarding its safety in real-clinical settings due to adverse drug reactions (ADEs). Hence the purpose of this study was to establish the prevalence and factors associated with adverse drug events among patients on dolutegravir-based regimen at the Immune Suppression Syndrome (ISS) Clinic- Mbarara Regional Referral Hospital (MRRH).Methods: A retrospective cross-sectional study was conducted at ISS Clinic-MRRH among 375 randomly selected patients who had been exposed to DTG-based regimen for at least 12 weeks. The patients were interviewed to obtain data on sociodemographics, dietary habits and thereafter their files reviewed to obtain data on ADEs. Data entry was done using Epi-data 3.0 and exported to SPSS version 25.0 for analysis. The prevalence of ADEs was determined as a percentage, and ADE associated factors were assessed using bivariate analysis, those found significant were further subjected to multivariate logistic regression model and were considered significant at P<0.05.Results: The prevalence of adverse drug events among patients on DTG-based regimen was found to be 33.1% (124/375) with 5.6% (7/124) participants discontinued from treatment due ADEs, 4 of which were due to hyperglycemia and 3 due to liver toxicity. The commonly experienced ADEs included abdominal pain, hyperglycemia and liver toxicity each at 7.3%, headache at 11.3%, and allergy at 36.3%. Male sex (AOR 1.571, 95% CI 1.433- 1.984), WHO stage one at entry to care (AOR 4.586, 95% CI 1.649-12.754), stage two (AOR 4.536, 95% CI 1.611-12.776), stage three (AOR 3.638, 95% CI 1.262-10.488), were significantly associated with ADEs. Patients with undetectable viral load at initiation of DTG-based regimen were less likely to experience ADEs (AOR = .324, 95% CI .1167-.629).Conclusions: Up to a third of patients on DTG-based regimen experienced ADEs. Male sex, WHO HIV disease stage and a detectable viral load at initiation of DTG-based regimen were significantly associated with ADEs. It is crucial to actively monitor patients with these characteristics for ADEs.