The primary purpose of this study was to assess the serum levels of homocysteine (HCY) at admission to the presence of post-stroke depression (PSD). From September 2014 to December 2015, first-ever acute ischemic stroke patients within the first 24 h after stroke onset were consecutively recruited and followed-up for 3 months. Based on the symptoms, diagnoses of depression were made in accordance with DSM-IV criteria for depression. By the time of 3 month after stroke, 238 had finished the follow-up and included in our study. Totally, 65 out of the 238 patients were diagnosed as depression (27.3%; 95% CI 19.6-35.4%). The results showed significantly higher HCY levels in patients with depression [21.4 (IQR 16.5-23.4) mmol/L vs. 14.1 (IQR 11.2-18.5) mmol/L, P < 0.0001) at admission than patients without depression. In multivariate logistic regression analysis, HCY was an independent predictor of PSD with an adjusted OR of 1.07 (95% CI 1.01-1.22; P = 0.013). Based on the ROC curve, the optimal cut-off value of serum HCY levels as an indicator for prediction of PSD was projected to be 16.5 mmol/L, which yielded a sensitivity of 82.5% and a specificity of 63.6%, with the area under the curve at 0.745 (95% CI 0.672-0.818; P < 0.0001). An increased risk of PSD was associated with serum HCY levels ≥16.5 mmol/L (adjusted OR 6.13, 95% CI 3.32-14.16; P < 0.001) after adjusting for above-recorded confounders. Elevated serum levels of HCY at admission were associated with depression 3-month after stroke, suggesting that these alterations might participate in the pathophysiology of depression symptoms in stroke patients. [ABSTRACT FROM AUTHOR]