Aims: We aimed to develop and test the psychometric properties of a Medical Device-related Pressure Injuries Knowledge and Practice Assessment Tool. Background: Assessment of nurses' knowledge and practices is critical in the prevention of Medical Device-related Pressure Injuries. Design: This was an instrument development and testing study. Methods: The sample of the study consisted of nurses (n = 189). The study was conducted in three phases between January and February 2021. In the first phase, multiple-choice items contained within Aetiology/Risk Factors, Prevention Interventions, and Staging domains were created. In the second phase, content validity and criterion validity were evaluated, and the tool was pre-tested. The third phase examined item difficulty, discrimination index and distractor quality. The test–retest method was used for reliability. Results: The Content Validity Index was found to be 0.75, 0.86 and 0.96 for the domains of Aetiology/Risk Factors, Prevention and Staging, respectively. The item difficulty values of the items were between 0.18 and 0.96. A positive, strong and significant relationship was found between the results and a positive, moderate and significant relationship between the tools administered for the proof of scale validity. The Cronbach's alpha reliability coefficient was found to be 0.54. Conclusions: The tool is a suitable measurement instrument for use in nursing education, research and clinical settings.