This systematic review aimed to compare the analgesic effectiveness and complications rates for anterior suprascapular nerve blocks (ASSB) compared to interscalene brachial plexus blocks (ISB) for arthroscopic and outpatient shoulder surgery. Only randomized controlled trials (RCTs) comparing the ASSB versus ISB in the context of arthroscopic shoulder surgery were eligible for inclusion. The primary outcomes included pain scores (Numeric Rating Scale of 0 to 10) up to 24 h postoperatively and analgesic consumption. Secondary outcomes included block complications. Meta-analysis was performed using random-effects modeling and result certainty was determined using the GRADEpro tool. Six RCTs (709 patients) were included for analysis. ISB displayed a statistically significant reduction in pain scores by 0.40 (95%CI = 0.36 to 0.45; p < 0.00001) but not morphine equivalent consumption (mean difference = 0.74 mg; 95%CI = − 0.18 to 1.66 mg; I2 = 60%; p = 0.11; moderate certainty) immediately in the postoperative care unit. Opioid consumption and pain scores at 6 to 24 h were not significantly different. There was no difference in respiratory events postblock. ASSB demonstrated a significantly lower incidence of Horner’s syndrome (relative risk (RR) = 0.17; 95%CI = 0.08 to 0.39; p < 0.00001; high certainty), voice hoarseness (RR = 0.24; 95%CI = 0.10 to 0.57; p < 0.00001; high certainty) and impaired respiratory function (p < 0.00001). The ASSB could be considered an appropriate analgesic option for arthroscopic shoulder surgery with potentially fewer complications than the ISB.