Aims: To identify the psychosocial adjustment of Turkish patients with breast cancer and the effects of perceived social support on their adjustment. Materials and Methods: The sample comprised 100 volunteering patients diagnosed with breast cancer in the last six months reporting to the Outpatient Chemotherapy Unit at the Medical Faculty Hospital in northern Turkey. The data for the study were collected through the Descriptive Information Form, the Psychosocial Adjustment to Illness Scale-Self-reflection (PAIS-SR) and the Cancer-Specific Social Support Scale and analyzed via SPSS 16.0 for Windows. Descriptive statistics, Chi square test, ANOVA and correlation were used to evaluate data. Results: There was a negative significant correlation between mean scores in the sub-scales of the social support scale and the ones in the sub-scales of the psychosocial adjustment to illness scale (p<0.05). Similarly, there was a negative significant correlation between confidence support and health care orientation as well as adjustment to social environment. Likewise, emotional support was in a negative significant correlation with health care orientation, adjustment to domestic environment, extended family relationships and adjustment to social environment. Conclusions: It was concluded that social support for patients with breast cancer had an influence on their psychosocial adjustment to illness. Holistic care should be given to breast cancer patients by oncology nurses especially in the first six months of treatment. It could be concluded that patients should be accompanied by their family/relatives in treatment and care following their diagnosis with breast cancer, that their family should be made more aware of the fact that the patient should be physically and psychologically supported, that patients with breast cancer should be provided with domiciliary care, and that they should be encouraged to participate in social support groups.