Posttraumatic growth is a positive psychological change that occurs as a result of tackling vital crises. Although cancer is perceived as a fatal disease, the individual's struggle with many negative conditions during diagnosis and treatment can provide positive change and development. The aim of this study was to examine the factor structure of the posttraumatic growth inventory (PTGI) in Turkish cancer patients. This study included 265 cancer patients receiving treatment at the chemotherapy unit of two university hospitals located in northern Turkey. Percentages, frequencies, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used to analyse the data, and Cronbach's alpha measured internal consistency. EFA yielded a five-factor structure: Spiritual and existential change, change in perception of life and selfness, relating to others, personal strength and new possibilities. Fit indices for CFA were root mean square error of approximation (RMSEA), 0.06; non-normed fit index (NNFI), 0.92; comparative fit index (CFI), 0.90; root mean residuals (RMR), 0.06; and goodness-of-fit index (GFI), 0.90. The overall Cronbach's alpha of the scale was 0.93. PTGI was determined as a reliable and valid tool for Turkish cancer patients. PTGI, which has a determined validity and reliability rate, can be used by healthcare professionals working with oncology patients to evaluate the positive psychological growth and changes in cancer patients and determine their adoption rate.