Medical device–related pressure injuries are a significant and largely preventable patient safety problem, yet existing pressure injury risk scales do not adequately capture device-specific risk factors in adults. This methodological study developed and psychometrically evaluated a standardized risk assessment scale to identify medical device–related pressure injury risk in hospitalized adult patients. An initial item pool was generated from an extensive literature review and clinical expertise, and content validity was assessed by seven experts using the Davis technique (content validity index = 0.96). The scale was administered to 160 adults receiving at least one medical device in medical, surgical and oncology wards and intensive care units of a university hospital. Construct validity was evaluated using binary logistic regression, exploratory factor analysis, and receiver operating characteristic curve analysis, demonstrating strong discrimination (area under the curve = 0.844, 95% confidence interval 0.728–0.961) with an optimal cut-off score of 14.5 (sensitivity 70.6%, specificity 88.8%). Exploratory factor analysis of the final version of the MedRAS (Kaiser-Meyer-Olkin = 0.792) revealed a two-factor structure (Device and Mechanical Factors; Patient and Tissue Factors) explaining 50.92% of the total variance, with all factor loadings above 0.30. The scale showed good internal consistency (Cronbach's alpha = 0.80) and very good inter-rater reliability (Cohen's kappa = 0.806, p < 0.001). This device-focused scale may support early risk identification and targeted preventive nursing interventions, with potential to improve patient safety and quality of care in inpatient/critical care settings.