Background: While BRCA testing is recommended for women diagnosed with breast cancer before age 50, little is known about decisions surrounding testing in young patients. Methods: As part of an ongoing cohort study, we surveyed 765 women diagnosed with breast cancer at age ≤ 40 about their experience with BRCA testing at approximately 1 year after diagnosis. We used Chi-square tests to evaluate differences in how genetic information was used to make treatment decisions among women who 1) tested positive 2) tested negative 3) were not tested. Among untested women, we assessed whether 1) genetic risk was discussed with a provider 2) reasons why they were not tested. Results: 655/765 (86%) of women reported undergoing BRCA testing by 1 year from diagnosis. 31% (232/746) said that knowledge/concern about genetic risk influenced treatment decisions. Among these women (Table), 87% of mutation carriers, 50% of non-carriers, and 45% of untested women chose bilateral mastectomy; fewer women reported that adjuvant treatment decisions were influenced by genetic risk concern. Among untested women, 32% (35/110) had not discussed the possibility that they might have a mutation with their doctor. The top 5 reasons cited for not testing were: patient perceived risk low (25%), doctor perceived risk low (24%), not a priority (18%), insurance/work (14%), financial (11%). 39% were thinking of testing in the future. Conclusions: >10% of women with breast cancer ≤ 40 were not tested for a BRCA mutation within a year of diagnosis. Among these women, 1/3 did not discuss genetic risk with their doctor. Given that knowledge/concern about genetic risk influences surgical decisions and can affect systemic therapy trial eligibility, all young breast cancer patients should have access to adequate genetic counseling and testing if desired.