IMPORTANCE: Disparities persist in testing and treatment for hepatitis C virus (HCV), leaving socially marginalized populations less likely to benefit from curative treatment. Linkage services are often insufficient to overcome barriers to navigating the medical system and contextual factors. OBJECTIVE: To determine the feasibility, acceptability, and safety of HCV treatment at the point of HCV infection diagnosis disclosure in a nonclinical community setting. DESIGN, SETTING, AND PARTICIPANTS: In this single-arm nonrandomized controlled trial conducted between July 1, 2020, and October 31, 2021, street-outreach recruitment targeted people experiencing homelessness and injecting drugs in an urban US community who were eligible for simplified HCV treatment. INTERVENTIONS: Study procedures were designed to reflect the community environment and services needed to provide HCV testing, disclosure, and treatment in a nonclinical site. The test-and-treat No One Waits (NOW) model of care provided a 2-week starter pack of 400 mg of sofosbuvir and 100 mg of velpatasvir at time of HCV RNA results disclosure. Participants were transitioned to insurance-provided sofosbuvir-velpatasvir when feasible to complete a 12-week treatment course. MAIN OUTCOMES AND MEASURES: The primary end point was sustained virologic response at posttreatment week 12 or later (SVR12). Acceptability end points were treatment initiation and completion. Safety end points were treatment discontinuation because of a late exclusion criterion and adverse events. RESULTS: Of the 492 people (median [IQR] age, 48 [37-58] years; 62 [71%] male) who underwent anti-HCV testing, 246 (50%) tested anti-HCV positive, and 111 (23%) tested HCV RNA positive and were eligible for simplified HCV treatment. Eighty-nine of the 111 eligible participants (80%) returned for confirmatory RNA results, and 87 (98%) accepted and initiated HCV treatment. Seventy (80%) were currently injecting drugs, 83 (97%) had an income below the poverty line, and 53 (61%) were currently unsheltered. Most had HCV genotype 1a (45 [52%]) or 3 (20 [23%]). Sixty-nine (79%) completed 12 weeks of sofosbuvir-velpatasvir treatment, 2 stopped treatment because of low adherence, and 16 were lost to follow-up. Of the 66 participants who completed treatment and had a successful blood draw, 61 (92%) had undetectable HCV RNA at treatment completion. Of the 87 treated patients, 58 achieved SVR12, leading to a treatment response of 67% (95% CI, 56%-76%) among the intention-to-treat group and 84% (95% CI, 73%-92%) among the per-protocol group. There were no adverse events, late exclusions, or deaths. CONCLUSIONS AND RELEVANCE: In this nonrandomized controlled trial of HCV treatment at the point of diagnosis, the NOW model of care reduced steps between HCV testing and treatment initiation and resulted in high levels of treatment initiation, completion, and cure. The NOW model of care can expand the current HCV test-and-treat toolkit by reaching a broader population of marginalized communities and expediting curative therapy. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03987503.