Metabolic syndrome prevalence in the United States rose from 27% to 34.2% between 1999-2000 and 1999-2006. However, prevalence has not been determined in the Military Health System. This retrospective descriptive study included enrolled Military Health System adults during fiscal years 2009-2012. We explored three populations (nonactive duty, active duty, and Air Force active duty) and their metabolic syndrome components (body mass index or waist circumference, blood glucose test, triglyceride, high density lipoprotein, and blood pressure). The active duty sample (who had all five components measured) was representative of its population, but the nonactive duty sample was not. Therefore, we reported component-wise prevalence for both nonactive and active duty populations, but only reported prevalence of metabolic syndrome for active duty. A decreasing trend, greater in men, was seen. Crude prevalence in 2012 was higher among men and highest among males and females aged 45-64. Only Air Force active duty data contained waist circumference measurements, enabling comparison to the United States. This subgroup prevalence was significantly lower than the United States prevalence in 2010 for both genders in every age group. Although decreasing metabolic syndrome prevalence is promising, prevalence is still high and future research should explore policies to help lower the prevalence.