This cross-sectional and correlational study was performed in order to determine the relationships between the perceived loneliness and social support levels of Turkish oncology patients, as well as their quality of life and symptom management. A total of 370 oncology inpatients participated in this study. Data were collected using, the FACT-G Quality of Life Scale, the Multi-Dimensional Scale of Perceived Social Support (MSPSS), the UCLA-Loneliness Scale (UCLA-LS), and the Edmonton Symptom Assessment Scale. A negative advanced significant relationship was found between the MSPSS total scores (r = -0.754, p < 0.01) and the UCLA-LS total scores. As the social support levels of the patients increased, their loneliness levels were seen to decrease and their quality of life was seen to increase. The patients were found to experience the symptoms of fatigue, worry, and feeling unwell more often as their loneliness levels increased and social support levels decreased.