Idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor T cell therapy, showed deep, durable responses in patients with triple-class exposed, relapsed and refractory multiple myeloma (RRMM) in the phase 2 KarMMa (Efficacy and Safety Study of bb2121 in Subjects With Relapsed and Refractory Multiple Myeloma) trial. We assessed health-related quality of life (HRQoL) among KarMMa patients. The European Organization for Research and Treatment of Cancer Quality of Life C30 Questionnaire and its supplementary 20-item multiple myeloma module, as well as the EuroQol 5-dimension 5-level instrument, were administered at screening, baseline (≤72 hours before or same day as lymphodepletion), day of ide-cel treatment, and after ide-cel treatment. Mean changes from baseline that exceeded the predetermined threshold of minimally important difference were deemed clinically meaningful. The proportions of patients experiencing clinically meaningful changes in HRQoL were assessed using within-patient change thresholds. Time to stable improvement (≥2 consecutive visits with clinically meaningful HRQoL improvements) was analyzed by using the Kaplan-Meier method. A total of 126 (98%) of 128 patients treated with ide-cel were included in the HRQoL analysis. Pretreatment baseline RRMM burden was high and meaningfully worse than that in the age- and sex-weighted general population. Statistically significant and clinically meaningful improvements from baseline were observed by month 1 for pain (-8.9) and disease symptoms (-10.2), and by month 2 for fatigue (-7.2), physical functioning (6.1), cognitive functioning (6.7), and global health status/QoL (8.0). Clinically meaningful improvements in fatigue, pain, and physical functioning were most prominent at months 9, 12, and 18, respectively, and were sustained through 15 to 18 months after ide-cel treatment. For triple-class exposed patients with RRMM with a poor prognosis and few treatment options, a single ide-cel infusion provides early, sustained, statistically significant, and clinically meaningful improvements in HRQoL. This study was registered at Clinicaltrials.gov as #NCT03361748.