Women with intellectual disability (ID) have similar rates of breast cancer as the general public, but higher breast cancer mortality and lower rates of regular screening mammography. Screening rates are lowest among women who live with their families. Though women with ID often make decisions in partnership with their relatives, we lack research related to family member perspectives on mammography. We conducted a qualitative study of family members of women with ID, with an interview guide focused on health care decision making and experiences, and breast cancer screening barriers, facilitators, and beliefs as related to their loved ones. Sixteen family members underwent semistructured interviews. Important themes included mammography as a reference point for other social and cultural concerns, such as their loved one's sexuality or what it means to be an adult woman; fear of having to make hard decisions were cancer to be diagnosed acting as a barrier to screening; a focus on quality of life; and desire for quality health care for their loved one, though quality care did not always equate to regular cancer screening. Adults with ID are valued members of their families, and their relatives are invested in their well-being. However, families fear the potentially complicated decisions associated with a cancer diagnosis and may choose to forgo screening due to misinformation and a focus on quality of life. Effective interventions to address disparities in mammography should focus on adults with ID and their families together, and incorporate the family context.