INTRODUCTION: With the scale-up of antiretroviral therapy (ART) there is a need to monitor programme performance to maximize ART efficacy and to prevent emergence of HIV drug resistance (HIVDR). In keeping with the elements of the World Health Organisation (WHO) guidance we carried out a nationally representative assessment of early warning indicators (EWI) at 304 randomly selected ART service outlets in Uganda. METHODS: Retrospective patient data was extracted for the six EWIs for HIVDR including; on-time antiretroviral (ARV) drug pick-up, patient retention on ART at 12 months, ART dispensing practices, ARV drug stock-outs, viral load suppression (VLS) and viral load (VL) testing completion. Point prevalence for each clinic and national aggregate prevalence with 95% confidence intervals (CI) for all clinics were estimated and facility performances were computed and association between EWIs and programmatic factors assessed using Fisher's Exact Test. RESULTS: Facilities meeting the EWI targets: on-time pill pick-up was 9.5%, more facilities in the north met this target (p = 0.040). Retention on ART at 12 months was 24.1%, facilities in Kampala region (p<0.001) and Specialized ART clinics (p = 0.01) performed better in this indicator. Pharmacy stock-outs was 33.6%, with more facilities in Kampala (p<0.001), specialized ART clinics (p<0.001) and private-for-profit (p<0.001) meeting this target. Dispensing practices was met by 100% of the facilities. VLS was met by 49.2% and 50.8% of facilities met VL completion target with facilities in central region performing better (p<0.001). National prevalence for the EWIs was: on-time pill pick-up 63.3% (CI: 58.9-67.8); retention on ART at 12 months 69.9% (CI: 63.8-76.0); dispensing practices 100.0%; VLS 85.2% (CI: 81.8-88.5) and VL completion, 60.7% (CI: 56.9-64.6). CONCLUSION: Dispensing practices in all facilities were in line with the national guidelines however, there still remains a challenge to long-term ART programmatic success in monitoring patient response to treatment, and maintaining patients on ART without interruptions arising due to poor patient adherence and as a consequence of ARV supply interruption. It is therefore of high importance that the national ART program ensures intensified follow-up for patients, ensuring uninterrupted supply of ARV drugs and increasing VL monitoring at treatment centres, in order to improve patient outcomes and avert preventable HIVDR.