Background The mid-upper arm circumference (MUAC) is a proxy for subcutaneous fat in the upper body and is a reliable screening measure for identifying individuals with abnormal local fat distribution. The purpose of this study was to evaluate the association between MUAC and metabolic syndrome (MetS) in middle-aged and elderly individuals. Methods We measured the MUAC in a cross-sectional sample with a total of 9787 subjects aged 40 years and older. 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 the 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. Results MUAC was positively correlated with waist circumference (r=0.437, P<0.001), BMI (r=0.334, P<0.001), fasting insulin(r=0.348, P<0.001), HOMA-IR (r=0.134, P< 0.001), triglycerides (r=0.138, P<0.001), SBP (r=0.124, P< 0.001), and DBP(r= 0.123, P<0.001), and inversely correlated with adiponectin (r=-0.147, P < 0.001) and HDL-cholesterol (r=-0.176, P<0.001) after adjusting for age and gender. Compared with the lowest quartile group, the odds ratios were substantially higher for MetS (OR 1.77; 95% CI 1.51-2.09, P for trend<0.001) in the highest MUAC quartile group after adjustment for potential cofounder. Conclusion Large mid-upper arm circumference is associated with metabolic syndrome in middle-aged and elderly individuals .