We evaluated in-hospital outcomes of acute coronary syndrome (ACS) patients with metabolic syndrome (MetS) in Oman. We analyzed the records of 1392 patients admitted with a diagnosis of ACS as part of the Gulf Registry of Acute Coronary Events. The prevalence of MetS among patients with ACS was 66%, with female preponderance (80% vs 57%; P < .001). MetS was associated with several characteristics including diabetes (45% vs 19%; P < .001), hyperlipidemia (40% vs 23%; P < .001), hypertension (62% vs 34%; P < .001), renal impairment (9.3% vs 3.4%; P < .001), Killip score > II (13% vs 8%; P = .004), and non-ST segment elevation myocardial infarction (78% vs 68%; P < .001). After multivariate adjustment, MetS was associated with higher risk of in-hospital heart failure (odds ratio [OR], 1.37; 95% CI: 1.03-1.81; P = .028) and mortality (OR, 4.42; 95% CI: 1.25-15.5; P = .020). Prevalence of MetS among patients with ACS in Oman is high. MetS was associated with higher in-hospital heart failure and mortality.