The Pittsburgh Sleep Quality Index (PSQI), a self-administrated questionnaire, is a frequently used instrument to assess sleep quality in clinical and non-clinical populations. The aim of the study was to evaluate the psychometric properties of the Arabic PSQI among patients diagnosed with cancer. A cross-sectional and descriptive correlational design was used with 369 patients with cancer completing the 19-item Arabic version of the PSQI. The scale was assessed in terms of acceptability, internal consistency and validity. The Cronbach’s alpha coefficient for the Arabic PSQI was 0.77, demonstrating acceptable reliability. The global PSQI score did not have floor or ceiling effects. The PSQI Arabic version demonstrated good discriminative validity. Construct validity was explored by confirmatory factor analysis to examine the dimensional structure of the PSQI. The confirmatory factor analysis showed an acceptable fit for refined one-factor model. The results support the original single factor structure of the PSQI. The Arabic version of the PSQI demonstrated adequate reliability and validity for assessing sleep quality in Arabic-speaking patients diagnosed with cancer.