Problem statement: “Back Apparatus: Collaboration between UKMMC with SOCSO” (BACKS) Tool is a Malay-language questionnaire-based tool to assess work-related chronic low back pain (LBP) in Malaysia. Purpose of study: This study provided internal structure evidence of construct validity of BACKS Tool in a sample of public hospital nurses in Malaysia. It was a preliminary study to development of an education module for nurses with LBP. Methods: A cross-sectional study was conducted involving nurses in six public hospitals in Penang, Malaysia. Job demands section (question 7) of the tool that forms part of final score, consists of two factors namely Physical Demand (5 items) and Psychological Demand (9 items). It was subjected to confirmatory factor analysis (CFA) to investigate the relationship between the items and the factors. Findings and results: A total of 1290 nurses completed the questionnaire. CFA by robust maximum likelihood estimation showed two- and one-factor models fit the data equally good (CFI and TLI>0.9, RMSEA<0.08, SRMR<0.06). However, the two-factor model showed multicollinearity between the factors (r=0.944). Conclusions and recommendations: There was poor discrimination between the physical and psychological demands based on the analysis. However, the discrimination can be justified based on the content of the items in the factors. Nevertheless, it is recommended to consider combining the factors into a single factor in future research.