Background: Both vitamin B12 and vitamin D are closely correlated with various neurological and psychiatric disorders. These vitamins might have an etiological and prognostic value across a variety of psychiatric illnesses, especially depressive disorder, anxiety disorder, substance use disorder, schizophrenia, dementia, schizophrenia, and so on. Objective: To explore about the deficiency of vitamin D and vitamin B12 in patients presenting to the psychiatry OPD and admitted in indoor wards and explore its relation with various psychiatric disorders. Materials and methods: In our cross-sectional, observational study, data were taken out retrospectively from the psychiatry and biochemistry record system of patients who had visited psychiatry OPD and IPD in the last 6 months and had undergone vitamin B12 and vitamin D investigations. Results: About 168 subjects were included in the study, of which 96 had undergone vitamin B12 level and 72 underwent vitamin D investigations. The mean of vitamin B12 was 314.02 ± 420.28 and the mean of vitamin D was 72.5 ± 62 in the study sample. Vitamin B12 deficiency was majorly found in patients suffering from anxiety disorder (29.8%) followed by depressive disorder (19.1%) and substance use disorder (17%), while vitamin D deficiency was mainly present in cases with an anxiety disorder (29.7%) followed by depressive disorder (13.5%). An equal number of cases with substance use disorder, schizophrenia, and somatic symptom disorder had the vitamin D deficiency. Conclusion: Early recognition of the deficiency and prompt management would surely affect the course of various psychiatric morbidities.