BACKGROUND: The incidence of non-Hodgkin lymphoma (NHL) in human immunodeficiency virus (HIV)-infected patients remains high despite treatment with antiretroviral therapy (ART). METHODS: We evaluated NHL incidence in HIV-infected patients followed in the Centers for AIDS Research Network of Integrated Clinical Systems who started combination ART and achieved suppression of HIV. We estimated the hazard ratio for NHL by time-varying HIV viremia categories, accounting for time-varying CD4 cell count using marginal structural models. RESULTS: We observed 37 incident NHL diagnoses during 21 607 person-years of follow-up in 6036 patients (incidence rate, 171 per 100 000 person-years; 95% confidence interval [CI], 124-236). NHL incidence was high even among patients with nadir CD4 cell count >200 cells/µL (140 per 100 000 person-years [95% CI, 80-247]). Compared with ≤50 copies/mL, hazard ratios (HRs) for NHL were higher among those with HIV viremia of 51-500 copies/mL (HR current = 1.66 [95% CI, .70-3.94]; HR 3-month lagged = 2.10 [95% CI, .84-5.22]; and HR 6-month lagged = 1.46 [95% CI, .60-3.60]) and >500 copies/mL (HR current = 2.39 [95% CI, .92-6.21]; HR 3-month lagged = 3.56 [95% CI, 1.21-10.49]; and HR 6-month lagged = 2.50 [95% CI, .91-6.84]). Current HIV RNA as a continuous variable was also associated with NHL (HR = 1.42 per log10 copies/mL [95% CI, 1.05-1.92]). CONCLUSIONS: Our findings demonstrate a high incidence of NHL among HIV-infected patients on ART and suggest a role of HIV viremia in the pathogenesis of NHL. Earlier initiation of potent ART and maximal continuous suppression of HIV viremia may further reduce NHL risk.