Antiretroviral therapy (ART) is recommended for all individuals with HIV infection, including those with acute HIV-1 infection (AHI). While recommendations are similar to those for chronic infection, efficacy data regarding treatment of acute HIV is limited. This was a single arm, 96-week study of a once-daily integrase inhibitor (INSTI)-based regimen using elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (EVG/COBI/FTC/TDF) in AHI. Primary endpoint was proportion of participants with HIV-1 RNA <200 copies/mL and <50 copies/mL by treatment weeks 24 and 48, respectively. We also examined time to viral suppression and weight gain after treatment initiation. Outcomes and characteristics were compared with a historical AHI cohort using a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen with efavirenz/emtricitabine/tenofovir disoproxil fumarate (EFV/FTC/TDF). Thirty-three participants with AHI were enrolled with 31 available for analyses. Most were African American (61%) and men who have sex with men (73%). Median age was 26 (IQR 22-42). Demographics were similar between the two AHI cohorts. By Week 24, 100% in the INSTI and 99% in the NNRTI cohort were <200 copies/mL; by Week 48, 100% in both cohorts were <50 copies/mL. Time to viral suppression was shorter in the INSTI cohort (median 54 versus 99 days). Mean weight change was similar with a 3.6 kg increase in the INSTI cohort and 2.4 kg in the NNRTI cohort at 96 weeks. INSTI-based ART during AHI resulted in rapid and sustained viral suppression. Over 96 weeks, weight increased in the INSTI-based cohort but was similar to weight increase in a historical NNRTI-based AHI cohort.