Egg proteins are important components for the development of functional foods and nutraceuticals. This study investigated the oxygen radical-scavenging effects of egg white protein ovotransferrin (including the whole protein, thermolysin–pepsin hydrolysate, and its bioactive peptides) and their interactions with four phytochemicals (vitamin C, epigallocatechin gallate (EGCG), caffeic acid, and quercetin), based on the oxygen radical absorbance capacity (ORAC) assay. The results showed that the hydrolysate possessed significantly higher oxygen radical absorbance capacity than the whole protein. The peptide IRW possessed very strong oxygen radical-scavenging effect, which might be attributed to its constitutive amino acid tryptophan (W) and the peptide bond between arginine (R) and W. Both the hydrolysate and the whole protein of ovotransferrin showed negative effects on four phytochemicals. However, the interactions between peptides/amino acids and the four phytochemicals are complex: some are positive, while others are negative. The results suggest that not only the phytochemicals, but also the hydrolysates or the peptides from the egg proteins could be a potential source of natural antioxidants.