Objective: This study evaluated the potential role of overall diet quality in the associations between ultraprocessed food (UPF) consumption and adiposity indicators among Korean adults. Methods: Baseline data of participants (n = 4331) of the Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) cohort study were obtained. Dietary information was collected by a validated food frequency questionnaire. UPF was defined using the NOVA classification. Overall diet quality was assessed using the Korean Healthy Eating Index. Adiposity indicators included BMI, waist circumference, percentage body fat by bioimpedance, and visceral fat mass by whole-body dual-energy x-ray absorptiometry. Mediation analysis after adjustment for potential confounders was performed. Results: UPF intake was associated with higher adiposity indicators after adjustment for confounders. The mediating effect of the Korean Healthy Eating Index on the relationship between UPF consumption and each adiposity indicator was 35.6% (95% CI: 4.9% to 255.9%) for BMI, 38.3% (17.9% to 132.1%) for waist circumference, 40.2% (8.3% to 259.4%) for percentage body fat, and 60.7% (−396.4% to 662.7%) for visceral fat mass. Conclusions: UPF consumption was positively associated with adiposity indicators, which were partially attributed to the overall diet quality. Further studies are needed to better understand the causal mechanisms of these associations.