Background: Metabolic syndrome (MS) is a cluster of cardiometabolic risk factors for future diabetes and cardiovascular diseases, and low grip strength (GS) is associated with an increased risk of MS. However, the index (among absolute GS, relative GS, and anthropometric indices) that is more strongly associated with MS has not been conclusively identified. Therefore, the objective of the present study was to simultaneously examine the associations of MS with relative and absolute GS and anthropometric indices in a Korean population. Methods: In this large-scale cross-sectional study, we used data from the Korean National Health and Nutrition Examination Survey (KNHANES). A total of 20,915 subjects were included in the statistical analyses. Complex sample binary logistic regression models were used to analyze the associations between MS and indices such as the waist-to-height ratio (WHtR), body mass index (BMI), and absolute and relative GS. Results: The prevalence of MS was 40.48% in men and 34.4% in women. The mean GS values in the healthy group and MS group were 38.06 ± 0.13 and 38.06 ± 0.15 years for men (p = 0.980) and 22.72 ± 0.07 and 21.19 ± 0.11 years for women (p < 0.001), respectively. Among all the indices, the WHtR was the index most strongly associated with MS in men. Among the GS indices, the GS/weight index was closely associated with MS, and the magnitude of this association was stronger than that of the absolute GS index. In women, the WHtR was the most related index to MS among all the indices. Among the GS indices, the GS/weight and GS/BMI indices were strongly associated with MS, and the magnitudes of these associations were much greater than those of the absolute GS index. Conclusions: Although absolute and relative GS indices are strongly associated with MS in the Korean population, the strongest association was observed for the simple anthropometric index (WHtR).