Background The mid-upper arm circumference (MUAC) is a proxy for upper body subcutaneous fat and a reliable screening measure for identification of individuals with abnormal local fat distribution. The purpose of present study was to evaluate the association between MUAC and metabolic syndrome (MetS) as well as other metabolic phenotype in the middle-aged and elderly population. Methods We measured the MUAC in a cross-sectional sample with a total of 9787 subjects aged 40 years and older in Shanghai, China. The measurement of MUAC is performed on the right arm using a non‐elastic tape held midway between the acromion and the olecranon processes in duplicate, with arm hanging loosely at the side of the body. The MetS was defined according to the Joint Statement of the International Diabetes Federation Task Force on Epidemiology and Prevention. The association of MUAC with MetS was tested in logistic regression analyses and reported as odds ratio (OR) with 95% confidence interval (CI). Results T he prevalence of MetS, overweight, and central obesity raised sharply from the smaller MUAC groups to the larger MUAC groups both in men and women. MUAC was positively correlated with waist circumference, BMI, fasting insulin, HOMA-IR, triglycerides, systolic and diastolic blood pressure, and inversely correlated with adiponectin and HDL-cholesterol after adjusting for age and gender. As the MetS components accumulated, the MUAC increased concomitantly. The risk of MetS in the highest MUAC quartile was significant higher (odds ratio 1.77; 95% confidence interval 1.51-2.09) than the lowest quartile after adjustment of potential confounders. Conclusion Our results indicated that large MUAC is an independent risk factor of MetS in Chinese individuals.