Extracranial-intracranial (EC-IC) bypass is an established technique to augment intracranial flow in patients with moyamoya disease (MMD) and other steno-occlusive diseases. The outcomes after direct EC-IC bypass for MMD compared to non-MMD pathologies (N-MMD) have not been systematically reviewed or compared in a meta-analysis. We performed a systematic review and meta‑analysis of studies reporting on outcomes in adults undergoing EC-IC bypass stratified by indication. Patients were assigned to either MMD or N-MMD pathologies with the latter primarily consisting of intracranial atherosclerotic disease (ICAD) and extracranial carotid occlusion (CO). Outcomes include graft patency, postoperative stroke or intracranial hemorrhage (ICH), and hyperperfusion syndrome (HPS). Random effects models were used to obtain pooled estimates for each outcome. Seventeen studies met inclusion criteria comprising 1,354 patients and 1,451 hemispheres. The weighted mean age was 49.1 years and 56.7% of patients were female. The indications for bypass included MMD or MMS in 52.6% of patients. ICAD and CO comprised 46.3% and 3.1% of patients, respectively. There was no difference in graft patency rates for the MMD and N-MMD groups (OR 0.81, 95% CI 0.54-1.21; I2 = 0%). There was also no difference in postoperative stroke (OR 0.68, 95% CI 0.33-1.41; I2 = 23%) or ICH (OR 1.46, 95% CI 0.34-6.26; I2 = 61.4%). There was no significant difference in the rate of HPS between the N-MMD and MMD groups (OR 1.69, 95% CI 0.67-4.26; I2 = 0). This meta-analysis discovered no significant differences in technical and postoperative outcomes between direct EC-IC bypass procedures performed for moyamoya and those performed for non-moyamoya steno-occlusive diseases. Further research with large multicenter cohorts, standardized techniques, and consistent outcome reporting is required to confirm these results.