Oat avenanthramides possess multiple biologically beneficial properties. However, their interaction with starch has not been investigated. This study aims to study the interactions between avenanthramides and starches using high-performance liquid chromatography, rapid viscosity analysis, and simulated digestion. Phenolic acids were employed as a comparative group. The results demonstrated that avenanthramides exhibited higher binding rates with gelatinized starches than phenolic acids, ranging from 92.9% to 99.8%. Moreover, avenanthramides decreased the viscosity, breakdown, and setback of corn starch. Furthermore, starches slightly increased the bioaccessibility of avenanthramide 2c. Additionally, avenanthramides decreased the contents of rapidly digestible starch and slowly digesting starch in corn starch while increasing resistant starch contents. Interestingly, avenanthramides exhibited a more pronounced delaying effect on starch digestion than phenolic acids, which can be attributed to their higher binding affinity with starch. This study provides the first demonstration of the significant inhibitory effect of avenanthramides on starch digestion.