Background: Breast cancer is worldwide the most common cancer in women and is a major public health problem. Genes with high or low penetrance are now clearly implicated in the onset of breast cancer, mostly the BRCA genes. All women in families at high risk of breast cancer do not develop tumours, even when they carry the familial mutation, suggesting the existence of genetic and environmental protective factors. Several studies have shown that consanguinity is linked to a decreased or an increased risk of breast cancer, but to the best of our knowledge, there is no study concerning the association between consanguinity and the occurrence of tumours in women with high risk of breast cancer. The objective of this study was to examine whether parental consanguinity in families with genetic predisposition to breast cancer affect the risk of siblings for having this cancer. Materials and Methods: Over a six-year period, 72 different patients with a histological diagnosis of breast or ovarian cancer from 42 families were recruited for genetic counselling to the Department of Medical Genetics, Rabat. Consanguinity rate was determined in cases and compared to the consanguinity rate in the Moroccan general population. Results: Consanguinity rates were 9.72% in patients and 15.3% in controls, but the difference was statistically not significant (p>0.001) and the mean coefficient of consanguinity was lower in breast cancer patients (0.0034) than in controls (0.0065). Conclusions: Despite the relatively small sample size of the current study, our results suggest that parental consanguinity in Moroccan women might not be associated with an altered risk of breast cancer. Large scale studies should be carried out to confirm our results and to develop public health programs.