Objective To describe clinical effectiveness of belimumab for systemic lupus erythematosus (SLE) in real-world practice in Argentina. Methods This retrospective, observational study analysed medical record data of patients with SLE treated with belimumab in 15 centres in Argentina. Primary endpoint: overall clinical response (assessed on a scale similar to the 6-point Physician Global Assessment) at months 6, 12, 18 and 24, all versus index (belimumab initiation). Secondary endpoints: improvement in disease activity (SELENA-SLEDAI), SLE manifestations, and corticosteroid dose change. Results Records for 81 patients (91% female) were analysed. Clinical improvements were reported for 95%, 95%, 98% and 100% patients at 6, 12, 18, and 24 months post index, respectively. Mean SELENA-SLEDAI score decreased from 11.21 at index to 4.76, 3.77, 3.86 and 2.17 at 6, 12, 18, and 24 months post index, respectively. Number of flares decreased from 1.05 at index to 0.21, 0.09, 0.22 and 0.30 at 6, 12, 18, and 24 months post index, respectively. Mean corticosteroid dose was 14.59 mg/day at index, and 6.45, 5.18, 5.17 and 4.78 mg/day at 6, 12, 18, and 24 months post index, respectively. Conclusions Real-world patients with SLE treated with belimumab in Argentina demonstrated clinical improvements and reductions in corticosteroid dose.