Introduction. The Objective Structured Clinical Examination (OSCE), an evaluation instrument, requires a validation process to guarantee the measurement of skills related to clinical reasoning. The OSCE is relevant for decision making during the formation process for professional practice. Objective. To determine the content validity and inter-rater reliability of an OSCE during a physiotherapy undergraduate programme for clinical reasoning. Materials and Methods. Instrumental design, which identified content validity through internal consistency (Cronbach’s alpha), added to recognition of the inter-rater reliability (intraclass correlation coefficient). Results. The instrument demonstrates good internal consistency and a degree of agreement from substantial to almost perfect. Conclusions. The OSCE proved a suitable instrument to assess the clinical reasoning skill in physiotherapy students; nevertheless, this validation process has limitations in the number of stations and in not having sufficient application to physiotherapy.