Identifying a BRCA mutation among families with hereditary breast and ovarian cancer enables distinguishing those who may benefit from a specific medical management. This study aimed to evaluate the uptake of predictive testing among close relatives of a proband in Spanish families with a BRCA1 or BRCA2 mutation, and to determine the associated demographic and clinical predictors. A retrospective cohort of families undergoing clinical genetic testing at four university hospitals in northeastern Spain was considered. From 108 unrelated BRCA1/2 families, 765 close relatives of probands were analyzed. Sixty percent of the first-degree and 28% of the second-degree relatives underwent predictive testing within a median time of 2 and 6 months, respectively, since the mutation disclosure to the proband. Relatives undergoing genetic testing were more likely to be female, first-degree, and belong to a family with a proband who had a high educational level. Relatives were also more likely to have offspring, a previous cancer diagnosis, and to be aged between 30 and 64 years. Among second-degree relatives, having a first-degree relative with cancer was highly correlated with uptake. In conclusion, uptake of BRCA1/2 predictive testing among close relatives was notably high and within a short period of time after disclosure of the mutation to the proband. Being female, a high educational level of the proband, and having a close relative with cancer were associated with uptake among relatives. Further studies are warranted to determine whether information is disseminated properly by probands and to learn about the reasons for those not undergoing testing.