We report magnetic resonance (MR) imaging findings of ductal carcinoma in situ (DCIS) within a fibroadenoma in a 42-year-old woman. Dynamic MR imaging revealed the mass to have 2 components with different kinetics. A nodular area within the mass showed faster initial enhancement followed by earlier washout and was histologically proven to be DCIS. Dynamic MR imaging reflected differences in vascularity between the fibroadenoma and DCIS, and parameter color maps generated from the dynamic data clearly demonstrated the extent of the DCIS.