BRCA1 mutation carriers are offered screening with MRI and mammography. Aim of the study was to investigate the additional value of digital mammography over MRI screening. BRCA1 mutation carriers, who developed breast cancer since the introduction of digital mammography between January 2003 and March 2013, were included. The images and reports were reviewed in order to assess whether the breast cancers were screen-detected or interval cancers and whether they were visible on mammography and MRI, using the breast imaging and data system classification allocated at the time of diagnosis. In 93 BRCA1 mutation carriers who underwent screening with MRI and mammography, 82 invasive breast cancers and 12 ductal carcinomas in situ (DCIS) were found. Screening sensitivity was 95.7 % (90/94). MRI detected 88 of 94 breast cancers (sensitivity 93.6 %), and mammography detected 48 breast cancers (sensitivity 51.1 %) (two-sided p < 0.001). Forty-two malignancies were detected only by MRI (42/94 = 44.7 %). Two DCIS were detected only with mammography (2/94 = 2.1 %) concerning a grade 3 in a 50-year-old patient and a grade 2 in a 67-year-old patient. Four interval cancers occurred (4/94 = 4.3 %), all grade 3 triple negative invasive ductal carcinomas. In conclusion, digital mammography added only 2 % to the breast cancer detection in BRCA1 patients. There was no benefit of additional mammography in women below age 40. Given the potential risk of radiation-induced breast cancer in young mutation carriers, we propose to screen BRCA1 mutation carriers yearly with MRI from age 25 onwards and to start with mammographic screening not earlier than age 40.