Introduction <p>Circadian syndrome (CircS) and metabolic syndrome (MetS) are thought to potentially affect cognitive function. We aimed to investigate the association between CircS/MetS and mild cognitive impairment (MCI).</p> Methods <p>Data was from two waves of the 2015 and 2018 China Health and Retirement Longitudinal Study. MetS defined by a harmonized standard, while CircS add depression and short sleep duration on MetS. Aging-related cognitive decline is used to define MCI. Next, participants without MCI at baseline were followed for 3 years. Multivariable linear regression and multiple logistic regression were used for the assessment. Finally, we further analyzed the association between CircS/MetS components and MCI.</p> Results <p>In the cross-sectional study (<i>N</i> = 11,719), CircS was associated with lower cognitive scores (β = -0.04, <i>P</i> &lt; 0.001) and higher risk of MCI (OR = 1.02, 95% CI: 1.00-1.04, <i>P</i> &lt; 0.05). MetS was not associated with either cognitive scores or MCI (<i>P</i> &gt; 0.05). In the longitudinal study (<i>N</i> = 8818), CircS increased the risk of MCI by 1.02-fold (95% CI:1.01–1.04, <i>P</i> &lt; 0.05), and MetS still did not show an association with MCI (<i>P</i> &gt; 0.05). In individual component analysis, short sleep (2015 ~ OR = 1.04, 95%CI: 1.02–1.05, <i>P</i> &lt; 0.001) and depression (2015 ~ OR = 1.04, 95%CI: 1.03–1.06, <i>P</i> &lt; 0.001; 2018 ~ OR = 1.03, 95%CI:1.01–1.05, <i>P</i> &lt; 0.01) were associated with a higher risk of MCI.</p> Conclusion <p>CircS is a risk factor for MCI in middle-aged and older adults, serving as a strong predictor of MCI, not MetS.</p>