The number of women treated with immunosuppressants is increasing. Often, these women are of childbearing age. Consequently, they must face the decision of whether to breastfeed when they do have a child. Although available studies recommend breastfeeding during immunosuppression, patients appear to need more knowledge to enable the decision-making process. This study aimed to investigate the knowledge of women after transplantation about breastfeeding during immunosuppression and their source of information. We performed a cross-sectional study from February 1 through August 31, 2022, with 45 female graft recipients (28 post-kidney and 17 post-liver transplantation) of childbearing age (15-49 years). The women were polled during their routine outpatient appointments and then divided into 2 groups: parous women (group 1, n = 26) and nulliparous women (group 2, n = 19). Most of the patients (84%) were administered tacrolimus-based regimens. Thirty-seven women voiced concerns about the possible harm to their babies through immunosuppressants in their breast milk (82%). The average score for knowledge of the benefits of breastfeeding was 51%; 58% in group 1, and 41% in group 2. Among parous women, 5 breastfed on immunosuppression, 15 did not, and the remainder did not take immunosuppression during breastfeeding. The decision regarding breastfeeding was influenced mainly by counseling from gynecologists (75%) and transplantologists (56%). Women's knowledge about the benefits of breastfeeding and the possibility of it during immunosuppression is not satisfactory.