Background: To examine the independent and combined association between relative quadriceps strength and the prevalence of type 2 diabetes mellitus (T2DM) in older adults. Methods: Among 1441 Korean older adults aged ≥65 years (71 [4.7] y) recruited between 2007 and 2016, 1055 older adults with no history of myocardial infarction, stroke, or cancer were included in the analysis. Cases of T2DM were identified by self-reported physician diagnosis, use antihyperglycemic medication or insulin, or fasting blood glucose ≥126 mg/dL. Logistic regression was used to calculate the odds ratios and 95% confidence intervals of T2DM by quartiles of relative quadriceps strength. Results: There were 162 T2DM cases (15%). Compared with the lowest quartile (weakest), the odds ratios (95% confidence intervals) of T2DM were 0.56 (0.34–0.90), 0.60 (0.37–0.96), and 0.47 (0.28–0.80) in the second, third, and fourth quartiles, respectively, after adjusting for possible confounders, including body mass index. In the joint analysis, compared with the “weak and overweight/obese” group, the odds (odds ratios [95% confidence intervals]) of T2DM was only lower in the “strong and normal weight” group (0.36 [0.22–0.60]) after adjusting for possible confounders. Conclusions: Greater relative quadriceps strength is associated with reduced odds of T2DM in older adults after adjusting for potential confounders including body mass index.