Objectives: This study examined whether a higher dietary inflammatory index (DII®) is associated with the risk of sarcopenic obesity (SO) and frailty among Korean older adults. Methods: A total of 950 participants aged 70–84 years, who completed the baseline nutrition survey of the Korean Frailty and Aging Cohort Study, were included in the analysis. The DII, quantifying the dietary inflammatory potential, was calculated using 23 foods and nutrients as assessed by a 24-h dietary recall. SO was defined as the coexistence of sarcopenia (dual-energy X-ray absorptiometry-measured appendicular skeletal muscle mass index of < 7.0 for males; <5.4 for females) and abdominal obesity (waist circumference of ≥ 90 cm for males; ≥85 cm for females). Frailty status was assessed using the Fried frailty index (range, 0–5), a simple tool for defining frailty that consists of three or more of five frailty items. Multinomial logistic regression models were used to estimate odds ratios (ORs) with 95% confidence intervals (CIs), adjusting for confounders. Results: The prevalence of SO and frailty was 9.8% and 10.8%, respectively. The DII was significantly higher in the frail group (2.7) compared to the robust and SO groups (2.0 vs. 1.8) (P < 0.001). Among nutrients and foods included in the DII, the frail group exhibited lower vitamin E, niacin, vitamin B6, energy, and protein intakes than the robust and SO groups. Multivariable-adjusted OR (95% CI) for frailty versus robust (comparing DII tertile 3 to tertile 1) was 2.3 (1.1–4.8; P-trend = 0.02). However, no significant association was observed between the DII and SO (OR, 1.1; 95% CI, 0.5–2.1; P-trend = 0.6). Conclusions: A higher DII score was associated with increased odds of frailty but not with SO in Korean older adults, suggesting that proinflammatory diets have a greater impact on frailty than that on SO in the older population.