Obsessive: Compulsive Disorder (OCD) is a chronic debilitating neuropsychiatric disorder, affecting 2% of global population and 0.6 % of Indian population. Treatment Refractory OCD (TR-OCD) is defined as poor response to serotonergic drugs, augmenting antipsychotics and behavioural therapy at optimal dose and duration. Various receptors involved in OCD are serotonergic, dopaminergic, glutaminergic (NMethyl-D-Aspartate - NMDA) and Gamma Amino Butyric Acid receptors. There is significant evidence regarding the role of serotonergic and dopaminergic receptors in neurobiology of OCD. Though the research in the role of glutamate and glutaminergic receptors in OCD is emerging, the current evidence regarding same is still limited. Along with this, research regarding the role of NMDA receptor inhibitors in treatment of OCD is also limited to few case reports. Ketamine is an inhibitor of the NMDA receptor. Ketamine has been used in treatment resistant depression. However, there is dearth of literature regarding use of ketamine in TR-OCD.