INTRODUCTION: This study aimed to examine the validity and internal consistency of Arabic version of the Cornell Scale for Depression in Dementia (A-CSDD) and compare it to the Geriatric Depression and Hospital Anxiety and Depression Scales. METHODS: Hundred fifty individuals were recruited; they underwent a clinical interview and filled the A-CSDD, Geriatric Depression Scale, and Hospital Anxiety and Depression Scale. The depression rating scales were validated against the Structured Clinical Interview for Diagnostic and Statistical Manual disorders. RESULTS: A-CSDD found to have sensitivity of 70%, specificity of 91%, and internal consistency of 0.89. The presence of depression was significantly associated with dementia. The associations of the A-CSDD with Arabic Geriatric Depression Scale (r: 0.3) and Arabic Hospital Anxiety and Depression Scale (r: 0.4) were lower in the demented group than in the nondemented group (r: 0.7 and 0.8, respectively). CONCLUSION: The diagnosis of depression in the context of dementia may be challenging. With this validated version, clinicians now have a tool helping them with the diagnosis.