Importance Supervised pelvic floor muscle training (PFMT) has been recommended as the first-line treatment for women with stress urinary incontinence (SUI), but more evidence on whether adjunctive methods would provide additional benefits is needed. Objective To compare the efficacy of PFMT with or without a home-based pressure-mediated biofeedback (BF) device. Design, Setting, and Participants This multicenter assessor-blinded randomized clinical trial was conducted in the obstetric clinics of 5 participating tertiary hospitals in China. Participants included eligible women with new-onset postpartum SUI who were enrolled from March 28, 2022, to October 13, 2023. Intervention All participants received 3 months of supervised PFMT and were randomized to either the intervention (PFMT with a home-based pressure-mediated BF device) or the control group (home-based PFMT). Main Outcome and Measures The primary outcome was the severity of urinary incontinence evaluated by the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form after 3 months of supervised PFMT. The secondary outcomes included the cure and improvement rates, PFM strength, quality of life, self-efficacy, and adherence. Results A total of 452 participants (median age, 34 [IQR, 31-36] years; median body mass index [calculated as the weight in kilograms divided by the height in square meters], 23.71 [IQR, 21.37-25.97]; median time since delivery, 50 [IQR, 43-61] days) were included in the analysis, with 223 in the intervention group and 229 in the control group. Compared with the control group, the intervention group achieved a significantly greater reduction in incontinence severity (median, 3.00 [IQR, 1.00-6.00] vs 2.00 [IQR, 0-4.00] points; z = -3.05; P = .002), significantly increased cure rate (45 of 223 [20.2%] vs 20 of 229 [8.7%]; z = 12.02; P = .001) and improvement (132 of 223 [59.2%] vs 102 of 229 [44.5%]; z = 9.71; P = .002), significantly greater pelvic floor muscle strength (median, 26.00 [IQR, 17.00-38.00] vs 21.00 [IQR, 13.50-33.50] cm H2O; z = -2.28; P = .02), and a significantly greater correlation between subjective and objective adherence (r = 0.825 vs r = 0.627). Conclusion and Relevance In this randomized clinical trial, the efficacy of pressure-mediated BF combined with PFMT was superior to that of PFMT alone. These findings support the use of pressure-mediated BF devices for improving treatment outcomes for patients with SUI. Trial RegistrationClinicalTrials.gov Identifier: NCT05115864