Corn is a major feedstock for the production of fuel ethanol as well as corn distillers grains that are widely used for animal feed. Corn is one of the most abundant sources of health-beneficial phytochemicals among crops. Little information is, however, available for phytochemicals in corn distillers grains. The objective was to determine amounts, availability, and antioxidant capacities of phytochemicals in corn distillers grains: dried distillers grains with solubles (DDGS), wet or modified wet distillers grains (WDG/MWDG), and condensed distillers solubles (CDS), compared with corn. Freeze-dried samples were extracted with 80% ethanol to obtain soluble phenolics. Residues were alkali-treated and extracted with ethyl acetate for cell-wall-bound phenolics. Amounts (total phenolic and flavonoid contents) and antioxidant capacities (DPPH radical scavenging, oxygen radical absorbance, hydroxyl radical averting, and iron chelating capacities) in both phenolics were evaluated. Phenolic acids and carotenoids were also identified and quantified using HPLC. Data were analyzed by ANOVA and sample means were compared using SNK multiple range test. Amounts and antioxidant capacities of soluble phenolics were the highest in DDGS, followed by CDS, WDG/MWDG, and corn (P < 0.05). Those of cell-wall-bound ones were the highest in DDGS, followed by WDG/MWDG, corn, and CDS (P < 0.05). Ferulic acid was the predominant phenolic acid (~90%) and its amount was the highest in DDGS (P < 0.05). Carotenoid content was the highest in DDGS, followed by WDG/MWDG, CDS, and corn (P < 0.05). Total phenolic, phenolic acid, and carotenoid contents in DDGS were over 3 times higher than in corn. It is known that, due to conversion of starch to ethanol and CO₂, macronutrients in corn are generally concentrated into DDGS over 3 times. The results indicate that phytochemicals in corn are well concentrated during the processing, thus DDGS have great potential as a source of phytochemicals to improve farm animal health and performance. However, cell-wall-bound phenolic contents in DDGS were 2–5 times higher than those of soluble ones, indicating that the majority of phenolics in DDGS are not readily absorbable. Hence, technologies to liberate them are needed to maximize health-beneficial potentials of DDGS.