Summary Introduction The increased incidence of young‐onset type 2 diabetes mellitus (YDM) is a major health problem. In this study, we tried to identify metabolic syndrome (MetS) components that could be used to predict YDM. Methods Thirteen thousand and nine hundred healthy young adults were enrolled and followed for 6‐117 months. The Cox proportional hazard model was used to identify which one of the MetS components can predict YDM. Logistic regression and receiver operating characteristic curve were applied to pinpoint the cut‐off points for the components. Results At the end of the follow‐up, 18 young adults developed YDM. It could be observed that men had a nonsignificant higher chance of developing YDM than women. Fasting plasma glucose (FPG) and waist circumference (WC) were the significant components which could predict YDM. The cut‐off points for FPG were 5.3 and 5.24 mmol/L for men and women and for the WC were 79.5 and 68.5 cm. After two equations were built by putting both WC and FPG together, the sensitivity did not change too much, but the specificity increased to 97.5%. Conclusions Among MetS components, FPG and WC are the two significant factors which can predict future YDM in young men and women. The cut‐off points of FPG and WC were lower than criteria of MetS. Using the same criteria in different age should be reconsidered.