The implication and clinical significance of low-level viremia (LLV) in HIV patients are still not clear. This study aimed to characterize the clinical outcomes and to evaluate whether LLV could predict future virological failure in a well-defined cohort of HIV-infected Omani patients attending a large HIV clinic. Patients on regular antiretroviral therapy (ART) for at least 12 months, and had at least 2 HIV RNA measurements 1 year after starting ART, were prospectively enrolled in a cohort study. LLV was defined as plasma HIV RNA between 50-200 copies/mL that persists after at least 2 consecutive measurements after 12 months of ART. Multivariate Cox proportional hazards regression model was used to measure the association among virological failure, LLV and potential predictors. After 12 months of starting ART, 60 patients (40%) had undetectable viral load (UVL) < 50 copies/mL, while 37 patients (24%) had LLV and 53 patients (35%) had primary virological failure > 200 copies/mL. The incidence rates of subsequent secondary virological failure for UVL and LLV groups, were 3 and 7 cases per 1000 patient-months, respectively. Compared to UVL group, LLV group had increased risk of subsequent secondary virological failure with hazard ratio of (4.437 [95% CI, 1.26-15.55]; p = 0.02). Age, duration of HIV infection, pretreatment HIV RNA level, pretreatment CD4+ cell count, and ART adherent were associated with subsequent secondary virological failure. Collectively, Omani HIV patients with LLV were at a higher risk for HIV virological failure, and should be monitored closely. Further studies are need to assess whether ART modification in LLV patients would lower the risk of virological failure.