Background: With the increased incidence of diabetes mellitus, the importance of early intervention in prediabetes has been emphasized. We previously reported that fermented kimchi, a traditional Korean food, reduced body weight and improved metabolic factors in overweight participants. We hypothesized that kimchi and its fermented form would have beneficial effects on glucose metabolism in patients with prediabetes. Methods: A total of 21 participants with prediabetes were enrolled. During the first 8 weeks, they consumed either fresh (1-day-old) or fermented (10-day-old) kimchi. After a 4-week washout period, they switched to the other type of kimchi for the next 8 weeks. Results: Consumption of both types of kimchi significantly decreased body weight, body mass index, and waist circumference. Fermented kimchi decreased insulin resistance, and increased insulin sensitivity, QUICKI and disposition index values (p = 0.004 and 0.028, respectively). Systolic and diastolic blood pressure (BP) decreased significantly in the fermented kimchi group. The percentages of participants who showed improved glucose tolerance were 9.5 and 33.3% in the fresh and fermented kimchi groups, respectively. Conclusions: Consumption of kimchi had beneficial effects on glucose metabolism-related and anthropometric factors in participants with prediabetes. Fermented kimchi had additional effects on BP and insulin resistance/sensitivity. The percentage of participants who showed improvement in glucose tolerance was high in the fermented kimchi group.