This study aims to explore how the families of patients with cancer respond to and act toward complementary and alternative medicine (CAM) use. A qualitative research design based on grounded theory was adopted in this study. Semistructured and face-to-face in-depth interviews were conducted. Each participant was involved in a one-to-one individual interview. Five categories emerged regarding how the families of patients with cancer responded to and acted toward CAM use: purposes of using CAM, CAM use between patients and families, role of family caregivers, actions when using CAM, and seeking religious practice. The core category following coding emphasized the paramount importance of patients' comfort. The findings revealed that the families of patients with cancer may respond and act differently regarding patients' use of CAM. During this process, patients may not inform family members that they are using CAM. Health care professionals should consider this in their interactions with family members.