Objective: The aim of the study is to adapt to Turkish the Functional Evaluation of Cancer Treatment-Breast (FACT-B) (version 4) Scale, which was developed to evaluate the quality of life of patients with breast cancer, and to evaluate its validity and reliability. Material and Methods: The sample of the methodological type study consisted of 185 women with breast cancer who were followed up after cancer treatment in the breast polyclinic of a tertiary public hospital. Data were collected between 1 August 2015 and 31 July 2016 with the FACT-B Scale and, for concurrent validity, the European Organization for Cancer Research and Treatment Quality of Life (EORTC QLQ-C30) and Breast Cancer-Specific Quality of Life (QLQ-BR23) modules. First, the linguistic equivalence of the scale was examined. After it was found to have linguistic equivalence, its structural validity was determined by confirmatory factor analysis (CFA). Concurrent validity, test-retest reliability, total-subscale correlations were tested with Pearson correlation analysis. Lower-upper group means and test-retest results based on the cut-off point were analyzed by Student’s t-test. The internal consistency of the scale items was evaluated with the Cronbach’s alpha coefficient. Results: The content validity index value of the scale was found to be 0.95. The FACT-B Turkish form was found to be in acceptable agreement with the original scale in CFA. It was found that the correlations of the scale with the EORTC QLQ-C30 and BR23 modules were significantly related, and the difference between the averages of the upper and lower 27% groups was significant (p<0.001). The Cronbach’s alpha coefficient of the scale showed good internal consistency, with rates ranging from 0.73 to 0.87, except for the breast cancer subscale (0.58). Test-retest reliability was supported by correlation coefficients between 0.708 and 0.930. Conclusion: The study findings showed that the Turkish version of the FACT-B Scale was a valid and reliable measurement tool. Thus, the scale can be used in clinical settings and studies in order to assess the quality of life of Turkish patients with breast cancer.