Background: Depression, a common mental disorder, has risen to be one of the leading causes of disability worldwide and a major cause of suicide attempts globally. There is evidence to suggest that magnesium affects the brain physiology and its role in NMDA (N-methyl-D-aspartate) receptor regulation makes it a factor of interest in depressive pathology. Aim __ampersandsignamp; Objectives: To estimate the Serum Magnesium in newly diagnosed patients of depression and to compare it with the normal population value. Methods: A cross-sectional study was conducted in the Department of Biochemistry and the Department of Psychiatry at MIMER Medical College, Bhausaheb Sardesai Talegaon Rural Hospital, Talegaon Dabhade, Pune patients were included. Their serum was collected before they started any medication, and was analysed for Magnesium level by xylitol blue method. Results: The serum magnesium levels are found to be significantly lower than the normal range. The mean value of serum Magnesium in the study group was 1.72__ampersandsignplusmn; 0.33 mg/dl, comparatively less than the population value of 2.1__ampersandsignplusmn; 0.26 mg/dl Conclusions: Serum Magnesium levels are decreased significantly in patients suffering from depression. Alteration of its level could play a role in the pathology of depression. There is a scope for use of magnesium level estimation to determine the level of depression and the efficacy of treatment. Use of Magnesium supplements in the treatment of depression may be effective and requires further research.