The effect of arthroscopic subacromial decompression for impingement syndrome is still under debate. The purpose of this study was to evaluate short-term and long-term effects of arthroscopic decompression in patients with subacromial impingement.A systematic literature search was performed in Pubmed, Embase, Scopus, Cochrane Library, and ClinicalTrials.gov through March 2021 to identify randomized controlled trials (RCTs) that evaluated the clinical effects of arthroscopic decompression versus placebo surgery or exercise therapy for patients with subacromial impingement. Outcomes were analyzed on an intention-to-treat basis with random-effects models.Nine RCTs were included in the meta-analysis. The pooled analysis showed that arthroscopic decompression was associated with significantly better function improvement at 24-36 months and ≥ 60 months (24-36 months: SMD: 0.29, 95% CI: 0.10 to 0.48, P = 0.002; ≥ 60 months: SMD, 0.65, 95% CI, 0.20 to 1.09, P=0.004) compared with control group. Moreover, the effect size of function improvement ≥ 60 months exceeded the minimum clinically important difference (MCID). Additionally, sensitivity analysis indicated that compared with either exercise therapy or placebo surgery, arthroscopic decompression was associated with significantly better function improvement ≥ 60 months follow-up. However, there was no significant difference regarding pain relief at 6 months, 12 months, 24-36 months, ≥ 60 months, and function improvement at 6 months, 12 months for arthroscopic decompression compared with control group.After ≥ 60 months of follow-up, arthroscopic decompression in patients with subacromial impingement appears to render better function results than exercise therapy and placebo surgery.I, systematic review and meta-analysis of level I studies.Copyright © 2022. Published by Elsevier Inc.