Objective: The aim of this study is to conduct a validity and reliability study of the Morning Stiffness Assessment Scale (MSAS) for patients with rheumatoid arthritis (RA) in the Turkish population. Methods: The sample of the study consisted of 112 patients who were diagnosed with RA and met the inclusion criteria, and who applied to the Internal Medicine-Rheumatology outpatient clinics of a university hospital. The research data were collected using a 16-question personal information form that inquired about the sociodemographic and disease-related characteristics of the patients, the MSAS, the Health Assessment Questionnaire, and the Visual Analog Scale through face-to-face interviews. Subsequently, the language and content, criterion, and construct validity, as well as the reliability analyses of the scale, were performed. Results: The Content Validity Ratio value was found to be 0.98. The item-total test correlation values of the scale were determined to range between 0.67 and 0.82. The Cronbach's alpha values for the sub-dimensions of the scale were calculated as 0.82 for factor 1, 0.91 for factor 2, and 0.92 for the total scale score. It was observed that the Turkish version of the scale showed good compatibility with the original model, confirming the two-factor structure of the scale. Conclusion: The Turkish version of the MSAS was found to be valid and reliable.