BRCA1 and BRCA2 play a central role in DNA repair and their germline pathogenic variants (gBRCA) confer a high risk for developing breast and ovarian cancer. Standard chemotherapy regimens for these cancers include DNA-damaging agents. We hypothesized thatgBRCAcarriers might be at higher risk of developing chemotherapy-related hematologic toxicity and therapy-related myeloid neoplasms (t-MN). We conducted a retrospective study of women newly diagnosed with invasive breast or ovarian cancer who were screened forgBRCA1/gBRCA2at Geneva University Hospitals. All patients were treated with (neo-)adjuvant chemotherapy. We evaluated acute hematologic toxicities by analyzing the occurrence of febrile neutropenia and severe neutropenia (grade 4) at day 7–14 of the first cycle of chemotherapy and G-CSF use during the entire chemotherapy regimen. Characteristics of t-MN were collected. We reviewed medical records from 447 patients: 58 gBRCA1and 40 gBRCA2 carriers and 349 non-carriers.gBRCA1carriers were at higher risk of developing severe neutropenia (32% vs. 14.5%,p= 0.007; OR = 3.3, 95% CI [1.6-7],p= 0.001) and of requiring G-CSF for secondary prophylaxis (58.3% vs. 38.2%,p= 0.011; OR = 2.5, 95% CI [1.4–4.8],p= 0.004).gBRCA2carriers did not show increased acute hematologic toxicities. t-MN were observed in 2 patients (1gBRCA1and one non-carrier). Our results suggested an increased acute hematologic toxicity upon exposure to chemotherapy for breast and ovarian cancer amonggBRCA1but notgBRCA2carriers. A deeper characterization of t-MN is warranted with the recent development of PARP inhibitors in frontline therapy ingBRCAbreast and ovarian cancer.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10689-023-00331-6.