The effect of high fraction of twin boundaries on radiation-induced segregation (RIS) in type 304 stainless steel (SS) was investigated using 4.8 MeV proton beam at 300 °C. Type 304 SS samples were irradiated to 0.86 and 1.00 displacement per atom (dpa) and characterization of RIS was done using Electrochemical Potentiokinetic Reactivation (EPR) tests at different depth from the surface. Localized attack on different microstructural features, grain and twin boundaries and in-grain pit-like features, was further evaluated by atomic force microscopy. The results clearly indicated that attack was mostly confined to twin boundaries, implying that the twin boundaries acted as a preferred defect sink.