Communication of familial risk of breast cancer and melanoma has the potential to educate relatives about their risk, and may also motivate them to engage in prevention and early detection practices. With the Health Insurance Portability and Accountability Act (HIPAA) privacy laws, the patient often becomes the sole communicator of such risks to family members. This study surveys mothers diagnosed with either breast cancer or melanoma and their adult children about their family communication style, knowledge of increased risk, and early detection practices. In both cancer groups, most mothers alerted their children of the risk and need for early detection practices. Breast cancer mothers communicated risk and secondary prevention with early detection by breast self-examination and mammograms whereas the melanoma mothers communicated risk and primary prevention strategies like applying sunscreen and avoiding deliberate tanning. Open communication about health matters significantly increased the likelihood that children engaged in early detection and/or primary prevention behaviors. Examining the information conveyed to at-risk family members, and whether such information motivated them to engage in early detection/prevention behaviors, is key to guiding better cancer prevention communication between doctors and patients.