Objective: To develop and test the content validity of the “Knowledge and Attitudes on Assessing Degrees of Physical Disability in Leprosy” instrument. Methods: Methodological study carried out between January and May 2019 in three stages: item generation, analysis of aggregated redundancy to the composition, and content validation, using the Delphi technique. Results: In the first evaluation, a relevance of ≥ 0.80 stood out for all items, except for 2.8, which was excluded. To make the instrument clearer, the sequence was renumbered from one to 32; 2.6, 3.1, and 15 were reformulated, and the others underwent modifications, except for ten and 13. After the second evaluation, all items obtained Content Validity Index > 0.90 and Kappa = 1.00. Conclusion: The instrument has an excellent content validity; it is inferred that it is adequate to measure the knowledge and attitudes of professionals in the assessment of physical disabilities in leprosy.