Purpose Patients with cancer are reported to experience high anxiety and depression related to their medical status. The current study aimed to investigate the effects of avoidance of cancer communication and of social support from family and medical professionals on the patients' anxiety and depression. Methods A national survey was conducted through regional branches of the National Cancer Center of South Korea, which yielded 296 patient–caregiver dyads. Patients' medical records complemented their self‐report survey data. Results Patients' anxiety was predicted by the family's avoidance of cancer communication and the level of emotional support from family. Patients' depression was predicted by the stage of cancer (Surveillance, Epidemiology, and End Results), the family's avoidance of cancer communication, the emotional support from family, and the medical professionals' respect. Interaction effects were not statistically significant. Conclusion The implications of the findings are discussed in terms of the psycho‐oncological and psycho‐social interventions. Copyright © 2016 John Wiley & Sons, Ltd.