BACKGROUND: In the phase 2 KarMMa trial, patients with relapsed/refractory multiple myeloma (RRMM) achieved deep and durable responses with idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor (CAR) T cell therapy. Here we report a sub-analysis of the Japanese cohort of KarMMa. METHODS: Adult patients with RRMM who had received  ≥ 3 prior treatment regimens, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 antibody, and had disease refractory to last treatment received ide-cel at a target dose of 450 × 10 CAR positive T cells. RESULTS: Nine patients were treated with ide-cel. The overall response rate was 89% (median follow-up, 12.9 months). The best overall response was stringent complete response in 5 patients (56%), very good partial response in 3 (33%), and stable disease in 1. Median duration of response was not reached. All patients experienced grade ≤ 2 cytokine release syndrome and one patient experienced grade 2 neurotoxicity, but all resolved. Two patients died, one each from plasma cell myeloma and general health deterioration. CONCLUSION: Ide-cel yielded deep, durable responses with a tolerable and predictable safety profile in Japanese patients with RRMM. These results are similar to those of the non-Japanese population in KarMMa.