Objective: Cascade genetic testing (CGT) of hereditary breast and ovarian cancer (HBOC) or Lynch Syndrome (LS) patients’ relatives offers opportunities to prevent cancer, but CGT rates are not well described. We aimed to measure reported disclosure of genetic testing results and CGT rates in these families and evaluate patients’ views of educational media. Methods: Patients with HBOC or LS identified from germline genetic testing at an academic institution between 2011 and 2016 were surveyed regarding disclosure, testing among relatives, and perceptions of educational materials. Medical records and pedigrees provided numbers of total and first-degree relatives. Results: Of 103 mutation carriers consented, 64 (63%) completed the survey an average of 38 months after receiving genetic testing results. Participants’ mean age was 53 years, and thirty-one (48%) had a cancer diagnosis. The majority (86%) felt extremely or very comfortable sharing health information. Participants disclosed results to 87% of first-degree relatives, but reported that only 40% of first-degree relatives underwent testing. First-degree female relatives had significantly higher CGT rates than first-degree male relatives (59% versus 21%, P < 0.001). Participants with HBOC reported higher CGT rates than those with LS (49% versus 33%, P = 0.02). Participants did not identify any one educational medium as more helpful than the others for disclosing results. Conclusion: Disclosure rates are high among HBOC and LS mutation carriers, but reported CGT rates are low. Gender- and mutation-specific barriers prevent patients’ family members from undergoing CGT. Future studies should implement materials to address these barriers and improve CGT rates.