CD30 expression is universal in anaplastic large-cell lymphoma and is expressed in some other peripheral T-cell lymphoma subtypes. Incorporation of brentuximab vedotin into initial therapy for people with CD30-positive peripheral T-cell lymphomas prolonged progression-free survival, but there is room for improvement, especially for people with non-anaplastic large-cell lymphoma subtypes. We conducted a multicentre, international, single-arm, phase 2 trial to evaluate the safety and activity of CHEP-BV (cyclophosphamide, doxorubicin, prednisone, brentuximab vedotin, and etoposide) followed by brentuximab vedotin consolidation in patients with CD30-expressing peripheral T-cell lymphomas across five academic centres in the USA and Canada. Adults aged 18 years or older with newly diagnosed, untreated CD30-positive peripheral T-cell lymphomas, Eastern Cooperative Oncology Group score of 0-2, and adequate organ function were eligible to receive six planned cycles of CHEP-BV (ie, 1·8 mg/kg brentuximab vedotin intravenously on day 1, cyclophosphamide 750 mg/m2 intravenously on day 1, doxorubicin 50 mg/m2 intravenously on day 1, etoposide 100 mg/m2 daily intravenously on days 1-3, and prednisone 100 mg daily orally on days 1-5) with prophylactic G-CSF. Patients who responded to the treatment could receive brentuximab vedotin consolidation for up to ten additional cycles either after autologous haematopoietic stem-cell transplantation (HSCT) or directly after CHEP-BV. The primary endpoints were unacceptable toxicity during a 3-plus-3 safety lead-in in participants who received study treatment and completed the safety evaluation period (to confirm the recommended phase 2 dose of brentuximab vedotin in CHEP-BV) and the complete response rate after CHEP-BV induction therapy in participants who received study treatment and had response evaluation. The study was registered at ClinicalTrials.gov (NCT03113500), and this cohort completed the trial. The trial is ongoing with the enrolment of a new cohort. 54 patients were screened for eligibility and 48 were eligible for the study. The participants (18 [38%] women and 30 [63%] men; 34 [71%] White, four [8%] Black, five [10%] Asian, ten [21%] Hispanic, and 37 [77%] non-Hispanic people) were recruited and enrolled between Dec 4, 2017, and June 14, 2021, and followed up until Aug 25, 2023, when the database was locked for analysis. 48 participants were evaluable for toxicity, and 47 were evaluable for response (one participant died from COVID-19 before response assessment). During the safety lead-in, one of six participants had an unacceptable toxicity (ie, platelet count <10 000 per mm3 in a participant with extensive bone marrow involvement), and the proposed phase 2 dose of 1·8 mg/kg brentuximab vedotin in CHEP-BV was confirmed. At completion of CHEP-BV, 37 of 47 participants had complete response, yielding a complete response rate of 79% (95% CI 64-89). The most common CHEP-BV-related toxicities of grade 3 or higher were neutropenia (14 [29%] of 48), leukopenia (11 [23%]), anaemia (ten [21%]), febrile neutropenia (ten [21%]), lymphopenia (nine [19%]), and thrombocytopenia (nine [19%]). There were no treatment-related deaths. In patients with mostly CD30-expressing peripheral T-cell lymphomas other than non-anaplastic large-cell lymphoma, CHEP-BV (with or without autologous HSCT) followed by brentuximab vedotin consolidation was safe and active. SeaGen, Leukemia and Lymphoma Society, Lymphoma Research Foundation, and the National Cancer Institute of the National Institutes of Health.