PurposeBRCA1andBRCA2tumors exhibit different characteristics. This study aimed to assess and compare the ultrasound findings and pathologic features ofBRCA1andBRCA2breast cancers. To our knowledge, this is the first study to examine the mass formation, vascularity, and elasticity in breast cancers ofBRCA-positive Japanese women.MethodsWe identified patients with breast cancer harboringBRCA1orBRCA2mutations. After excluding patients who underwent chemotherapy or surgery before the ultrasound, we evaluated 89 cancers inBRCA1-positive and 83 inBRCA2-positive patients. The ultrasound images were reviewed by three radiologists in consensus. Imaging features, including vascularity and elasticity, were assessed. Pathological data, including tumor subtypes, were reviewed.ResultsSignificant differences in tumor morphology, peripheral features, posterior echoes, echogenic foci, and vascularity were observed betweenBRCA1andBRCA2tumors.BRCA1breast cancers tended to be posteriorly accentuating and hypervascular. In contrast,BRCA2tumors were less likely to form masses. In cases where a tumor formed a mass, it tended to show posterior attenuation, indistinct margins, and echogenic foci. In pathological comparisons,BRCA1cancers tended to be triple-negative subtypes. In contrast,BRCA2cancers tended to be luminal or luminal-human epidermal growth factor receptor 2 subtypes.ConclusionIn the surveillance ofBRCAmutation carriers, radiologists should be aware that the morphological differences between tumors are quite different betweenBRCA1andBRCA2patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10396-023-01296-w.