Objective Kimchi is a traditional Korean food. Kimchi, especially in its fermented form, is found to reduce body weight and improve metabolic parameters in overweight and obese patients. However, research about the effects of Kimchi in patients who show abnormality in glucose metabolism is lacking. The aim of this study is to investigate the beneficial effects of Kimchi on glucose metabolism in patients with prediabetes. Methods Nineteen patients, diagnosed with prediabetes according to the criteria of the American Diabetes Association (100 ≤ fasting glucose < 126 mg/dL or 140 ≤ 2-hour post-load glucose < 200 mg/dL), were enrolled. They were randomly assigned to an 8-week diet phase. During the diet phase, the subjects consumed either fresh or fermented Kimchi which were created from the same standardized recipe and ingredients. The Kimchi differed in terms of fermentation. One-day-old and 10-day-old Kimchi were defined a ”fresh” and “fermented”, respectively. A percentage of patients who showed an improved glucose metabolic status were analyzed. Results In the fresh Kimchi group, 2 of 8 (25%) showed improved glucose metabolism status. Of the two patients with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), one of them showed improved IFG and the other showed improved IGT after ingestion of fresh Kimchi for 8 weeks. In the fermented Kimchi group, 7 of 11 (63.6%) represented improved glucose metabolism status. Among the 7 patients who showed improvement, 5 patients with IFG and/or IGT showed normal glucose tolerance (NGT) after ingestion of fermented Kimchi for 8 weeks. Conclusion After ingestion of fresh or fermented Kimchi for 8 weeks in prediabetes patients, 25% and 63.6% showed improved glucose metabolism status, respectively.