In this study, a dual-mode sensing system was developed for the determination of total antioxidant capacity (TAC) using the Fe(III)-phenanthroline (Fe(III)-phen) reagent. The first detection mechanism of the system is based on the reduction of the Fe(III)-phen reagent by antioxidants, leading to the formation of the orange-red Fe(II)-phen chelate, which is quantified by the absorbance change at 510 nm. The second mechanism exploits the oxidase-like activity of the Fe(III)-phen complex. This complex generates superoxide anion radicals that oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue-colored oxidized TMB (ox-TMB) charge-transfer complex. In the presence of antioxidants, this reaction is inhibited, resulting in a decrease in ox-TMB formation, and the absorbance change at 652 nm correlates with the TAC of the tested sample. The proposed system was successfully applied to standard antioxidants, synthetic antioxidant mixtures, and real food extracts, demonstrating its applicability and sensitivity for TAC analysis. The linear equation of the calibration graphs obtained for different trolox (TR) concentrations were found to be A