CHA2 DS2 -VASc score has been proven to have great prognostic value in patients with acute coronary syndrome (ACS). We aimed to determine whether the addition of renal dysfunction in the CHA2 DS2 -VASc score would improve the prognostic impact of the scoring system to predict prognosis among ACS patients. A total of 3031 ACS patients were prospectively enrolled at 39 hospitals and followed for 1 year. The patients were divided into three groups based on estimated glomerular filtration rate (eGFR) (group 1, eGFR>90; group 2, eGFR between 60 and 90; and group 3, eGFR<60 mL/min per 1.73 m(2) ). The occurrence of subsequent myocardial infarction (MI), stroke, or death was recorded. As renal function progressively decreased from group 1 to 3, the patients were, respectively older and had higher incidence of comorbidity, worse Killip classification, and less evidence-based medical therapies. The rate of subsequent MI, stroke or death increased from 3.4% in group 1 to 7.4% in group 2 and 17.2% in group 3 (P <0.001). Renal dysfunction (eGFR<60 mL/min per 1.73 m(2) ) and CHA2 DS2 -VASc scores were both significant predictors of adverse events in multivariable regression analyses. Renal dysfunction can further stratify patients with CHA2 DS2 -VASc score of 0 or 1 into 3 groups with different adverse event rates (group 1, 3.0%; group 2, 4.1%; and group 3, 9.2%, P <0.001). A new scoring system (R-CHA2 DS2 -VASc score) derived by assigning one more point for eGFR ≤ 60 mL/min per 1.73 m(2) to the CHA2 DS2 -VASc score could improve its predictive accuracy (area under the receiver operating curve, 0.70 vs. 0.66, P <0.001). Renal dysfunction is a significant risk factor of future adverse events in ACS patients and may improve the prognostic impact of the CHA2 DS2 -VASc score.