Type-2 diabetes mellitus (T2DM) is strongly associated with various complications, including cognitive impairment. Diabetic complication is related with structural and functional changes of brain. Studies investigated that homocysteine as an independent risk factor of several organ complications. This marker might have a role in pathogenesis of cognitive impairment in T2DM patients. We aimed to know the association between serum homocysteine level and cognitive impairment in middle-aged T2DM populations. The study was a cross-sectional study involving 97 T2DM patients aged <60 years old. Cognitive assessment was based on validated Indonesian version of Montreal Cognitive Assessment (MoCA-INA) test. Besides, serum homocysteine level (Hcy) was measured based on standard laboratory assay. Filling out the questionnaire of MoCA-INA was conducted when patients came to take the blood sample. This study used independent t-test, chi-square and multivariate logistic regression model to analyze the data. There were 47 subjects (48.5%) with mild cognitive impairment (MCI). Delayed recall was the most impaired domain (94.8%). There was no significant mean difference of serum Hcy level in MCI and non-MCI group (11.99±3.27 μmol/L vs 12.36±4.07 μmol/L respectively, p = 0.62). Final model of logistic regression showed no association between serum Hcy and cognitive function after adjusting confounding variables (OR: 1.778; 95%CI: 0.69–4.54). Further investigation involving slight elderly T2DM patients with larger sample size should be conducted to confirm this finding.