Objective <p>To develop and validate a measurement instrument aimed at assessing the prevalence of psychiatric medication use among final-year dental students enrolled in Brazilian universities. Methods: The process emphasized both the construction of the questionnaire and the collection of evidence for its content validity. A mixed-methods approach was employed, integrating quantitative and qualitative methodologies. The initial stages involved defining the main research problem, establishing the instrument’s objectives, determining its conceptual domains, identifying the target population, and constructing the items, scoring system, and response scales. Based on a comprehensive literature review, a preliminary questionnaire consisting of 23 open- and closed-ended items was created. This version was submitted to a panel of eight expert judges—academics and/or researchers specializing in Psychology, Psychiatry, Pedagogy, and Dentistry/Instrument Development—tasked with evaluating each item’s clarity. Results: Content analysis was conducted using consensus thresholds. Quantitatively, the agreement rate among judges was calculated as the proportion of experts endorsing each item. Items with less than 90% agreement were revised; items with 90% or greater agreement were considered acceptable. In the first round of evaluation, 14 items were rejected. After modification based on judge feedback, all items were approved in the second round. The high level of agreement among experts was deemed sufficient to provide evidence of content validity. Following expert validation, a pre-test was conducted with dental students’ representative of the target population. Based on both qualitative and quantitative feedback, two questions were adjusted, leading to the development of the final version of the instrument. Conclusions: These initial findings and methodological steps form the foundation for the instrument’s definitive application in future research assessing psychiatric medication use among undergraduate dental students.</p>