Introduction The Work Ability Index questionnaire (WAI) assesses the perception of the worker in relation “how well a worker is or will be in the present or near future and how capable this worker is of performing work given the demands of the job and the health status and mental and physical capabilities of the worker.” Aims: to investigate the validity and reliability of the WAI in 1436 nurses' work of tree public hospital of the Rio de Janeiro.

Methods We evaluated the validity dimensional through exploratory factor analysis using polychoric correlation matrix and parallel analysis for retention of factors and correlational validity correlating the WAI with theoretically relevant constructs using Spearman correlation. The reliability was assessed by the Cronbach's α and McDonald's ω coefficients. The factorability of data was tested by the Meyer-Olkin index (KMO) and Bartlett's Test of Sphericity. The R software was used for analysis.

Results The factorial analyses indicated a two-dimensional structure (perception of work ability/mental resources and diseases and health restrictions). The value of Cronbach's α and McDonald ω was, respectively, 0.80 and 0.87. The theoretical hypothesis of the construct validity were confirmed with direct correlation and significant of the WAI with the scores of reward, control and self-evaluate of the health status; inverse correlation and significant with the scale of need for recovery, psychological distress, effort, over-commitment and demand.

Conclusion We found good evidence for a high reliability and construct validity of WAI questionnaire, supporting its use in future analyses in similar populations.