Background: This study evaluated the effectiveness of treatment with an indapamide/amlodipine single-pill combination (SPC) in outpatients with uncontrolled isolated systolic hypertension (ISH) aged over 55 years in real-life clinical practice. Methods: This was a post-hoc analysis of the subgroup of patients with ISH from ARBALET, a 3-month, multicenter, observational, open-label study conducted in Russia among patients with grade I or II hypertension who were either uncontrolled on previous antihypertensive treatment or treatment-naïve. The effectiveness of indapamide/amlodipine SPC was assessed by the change in office systolic blood pressure (SBP) and the rate of target SBP (< 140 mmHg) achievement at 2 weeks, 1 month and 3 months, in four age groups: 55–59 years, 60–69 years, 70–79 years, and 80 years or older. Results: The ARBALET study recruited 2217 patients, of whom 626 had ISH and were included in this post-hoc analysis (mean age 66.1 ± 7.8 years; 165 men [26.4%] and 461 women [73.6%]). Target SBP < 140 mmHg was achieved in 43%, 75% and 93% of patients at 2 weeks, 1 and 3 months, respectively. SBP decreased from baseline by 18.8 ± 10.5 mmHg, 27.2 ± 10.6 mmHg and 31.8 ± 9.9 mmHg at 2 weeks, 1 month and 3 months, respectively. In the groups of patients aged 55–59, 60–69, 70–79, and ≥ 80 years, SBP reductions at 3 months compared with baseline were − 30.3 ± 9.4, − 32.4 ± 9.7, − 32.5 ± 10.7, and − 28.9 ± 9.6 mmHg, respectively. Conclusion: This post-hoc analysis of the observational ARBALET study showed that indapamide/amlodipine SPC was associated with significant reductions in BP and high rates of target BP achievement in a broad age range of patients with ISH treated in routine clinical practice. Study registration number: ISRCTN40812831. © 2022, The Author(s).