BACKGROUND: In low-income and middle-income counties (LMICs), the outcome of relapsed or refractory B-cell malignancies is poor due to the absence of effective therapies. We report the results of a phase 1/2 study of a novel humanised anti-CD19 4-1BB chimeric antigen receptor (CAR) T-cell therapy, talicabtagene autoleucel, for patients with relapsed or refractory B-cell malignancies. METHODS: This open-label, multicentre, phase 1/2 study was done at six tertiary cancer centres in India. Phase 1 was a single-centre study done in Tata Memorial Hospital, India, in patients aged 18 years or older with relapsed or refractory B-cell lymphomas. Phase 2 was a single-arm, multicentre, basket trial done in five tertiary cancer centres in patients aged 15 years and older with relapsed or refractory B-cell acute lymphoblastic leukaemia or B-cell lymphoma. Eligible patients had a life expectancy of 12 weeks or more, an ECOG performance status of 0-1 (phase 1) or 0-2 (phase 2), and an adequate organ function. Patients underwent apheresis to obtain at least 1 × 10 FINDINGS: Of 64 patients, 14 were enrolled in phase 1 (from May 11, 2021, to May 13, 2022) and 50 were enrolled in phase 2 (Dec 27, 2022, to Aug 31, 2023). The median age of the overall cohort was 44 years (IQR 27-57), and 49 (77%) of 64 patients were male and 15 (23%) were female. In phase 1, no dose-limiting toxicities occurred at doses of 2 × 10 INTERPRETATION: Talicabtagene autoleucel had a manageable safety profile and induced durable responses in patients with relapsed or refractory B-cell malignancies. This therapy addresses an important unmet need for patients with relapsed or refractory B-cell malignancies in India. FUNDING: Immunoadoptive Cell Therapy (ImmunoACT) and Indian Council of Medical Research (ICMR).