Purpose The International Classification of Functioning, Disability and Health (ICF) has proven to be a valuable framework for vocational rehabilitation (VR). No reliable and valid ICF-based instruments to capture work functioning is known, hence, the aims of this study were: (1) to outline the process for developing an ICF-based questionnaire, the Work Rehabilitation Questionnaire (WORQ) to assess functioning in VR and (2) to report preliminary psychometric evidence. Methods ICF categories were selected from the ICF Core Sets for VR using explorative Rasch-analysis and VR literature review. Questions were worded to assess identified ICF categories. WORQ was translated from English to German. Psychometrics for the German version of WORQ was examined in one VR centre in Switzerland. Results 44 ICF categories were selected which resulted in 36 questions related to functioning. The psychometric evaluation of WORQ showed high test–retest reliability (Spearman correlation 0.79) (n = 53) and good internal consistency (Cronbachs Alpha 0.88) (n = 74) WORQ showed moderate correlation with Beck Depression Inventory II (Spearman correlation 0.511) and low correlation (Spearman correlation −0.353) with SF-36. Conclusions WORQ appears to be a reliable, ICF-based questionnaire to evaluate functioning in VR, easy to administer by health or vocational professionals. The additional information gained when using WORQ would contribute to improving interdisciplinary understanding of the patient’s situation and therefore support the integrative planning of the return-to-work process or engagement in gainful employment. However, further studies are needed to further examine its use in clinical practice and research, when validated in other patient populations and settings.