Diabetes and psychiatric disorders have a bidirectional association and they influence each other in number of ways. The psychiatric disorders are relevant with diabetes includes delirium, substance use disorders, depression, anxiety and psychotic illness like schizophrenia. The co-occurrence of diabetes and depression has been proved in clinical as well as general population studies. Delirium in diabetes occurs as hypoactive or hyperactive delirium but most of patients experience hypoglycemic delirium. The substance abuse such as tobacco and alcohol will influence smoking-induced hyperglycemia and drug-induced hypoglycemia in susceptible individuals. Mood disorders include depressive disorders, dysthymia and bipolar affective disorders are associated with diabetes, it can be treated with psychotropic medications. The commonly used medications for depression are tricyclic antidepressants, SSRIs, selective serotonin and norepinephrine reuptake inhibitors and serotonin modulators. The co-occurrence of psychiatric disorders in diabetes affects the quality of life, increased cost of care, poor treatment adherence, poor glycemia control and higher rate of absenteeism. The two nosological systems used for the diagnosis of psychiatric disorders are also discussed in this chapter.