Occupation can influence the prevalence of metabolic syndrome. Age and gender could interact with the association between occupation and metabolic syndrome. This study aimed to investigate the prevalence of metabolic syndrome among the Korean working population and determine whether the prevalence differed according to occupation, age and gender. We conducted a cross-sectional study in Korean adults using the Third Korean National Health and Nutrition Examination Survey (KNHANES III). The analysis included 3,288 workers over 19 yr old. The prevalence odds ratios (PORs) of metabolic syndrome among representative types of occupations were estimated after stratification for age and gender by logistic regression. Female manual workers had a higher prevalence of metabolic syndrome than female non-manual workers among those younger than age 50 (POR=1.95, 95%CI=1.12–3.40). However, female manual workers aged 50 and older had a lower prevalence of metabolic syndrome than female non-manual workers (POR=0.36, 95%CI=0.22–0.59). Manual occupations can be a risk factor for metabolic syndrome, but this correlation is limited to younger female workers. The effects of occupation on the prevalence of metabolic syndrome were different between older and younger workers, which could be due to longitudinal transition of socio-cultural structure.