Background: Population-scale evidence for the association between dynamic changes in metabolic syndrome (MetS) status and alterations in the risk for major adverse cardiovascular events (MACE) is lacking. Objective: To investigate whether recovery from or development of MetS in a population is associated with an altered risk for MACE. Design: Nationwide cohort study. Setting: An analysis based on the National Health Insurance Database of Korea. Participants: A total of 27 161 051 persons who received national health screenings from 2009 to 2014 were screened. Those with a history of MACE were excluded. We determined the MetS status of 9 553 042 persons using the following harmonizing criteria: MetS-chronic (n = 1 486 485), MetS-developed (n = 587 088), MetS-recovery (n = 538 806), and MetS-free (n = 6 940 663). Measurements: The outcome was the occurrence of MACE, including acute myocardial infarction, revascularization, and acute ischemic stroke, identified from the claims database. The incidence rate ratios (IRRs) were calculated with adjustments for body mass index, comorbidity scores, previous metabolic variables, and other clinical or demographic variables. Results: At a median follow-up of 3.54 years, the MetS-recovery group (incidence rate, 4.55 per 1000 person-years) had a significantly lower MACE risk (adjusted IRR, 0.85 [95% CI, 0.83 to 0.87]) than that of the MetS-chronic group (incidence rate, 8.52 per 1000 person-years). The MetS-developed group (incidence rate, 6.05 per 1000 person-years) had a significantly higher MACE risk (adjusted IRR, 1.36 [CI, 1.33 to 1.39]) than that of the MetS-free group (incidence rate, 1.92 per 1000 person-years). Among the MetS components, change in hypertension was associated with the largest difference in MACE risk. Limitation: Limited assessment of mortality and short follow-up. Conclusion: Recovery from MetS was significantly associated with decreased risk for MACE, whereas development of MetS was associated with increased risk.