Background: Patients with Alzheimer disease (AD), the most common form of dementia. The present study was conducted to assess effectiveness of vitamin D supplements in the patients suffering from Alzheimer disease. Materials & Methods:60 patients of Alzheimer disease of both genders were divided into 3 groups of 20 each. Group I were prescribed memantine alone, group II were prescribed vitamin D alone and group III were prescribed memantine plus vitamin D for 6 months. Cognitive change with the mini-mental state examination (MMSE) was assessed. Results: Group I had 20 males and 10 females, group II had 12 males and 18 females and group III had 16 males and 14 females. The mean MMSE score before treatment in group I was 16.8 and after treatment was 16.4, in group II before treatment was 18.3 and after treatment was 17.5, in group III before treatment was 13.4 and after treatment was 17.2. The difference was significant (P< 0.05). Conclusion: Patients who took memantine plus vitamin D had a statistically and clinically relevant gain in cognition as compared to memantine and vitamin D alone.