Introduction Blood dyscrasias can occur secondary to antipsychotic drug use which may be due to direct drug toxicity or immunologic mechanisms causing bone marrow suppression. Antipsychotic use mostly causes neutropenia and less frequently thrombocytopenia. Drug-induced pancytopenia is a very rare side-effect of psychotropic medications and is even rarer with butyrophenones like haloperidol Methods We reviewed the case of a geriatric patient who developed pancytopenia while on haloperidol decanoate monthly injection Results We present the case of an 85-year-old African-American woman with a long history of schizophrenia, who was stabilized on Haloperidol Decanoate 50?mg monthly IM for a few years at another hospital. She was then maintained on the Haloperidol decanoate for a few months after she moved outpatient care to our hospital. She was noted to have pancytopenia at initial presentation in the clinic and her RBC, Platelets, and WBC (including neutrophil) counts gradually declined to the point where her Haloperidol Decanoate was placed on hold in order to further monitor the blood counts. Baseline leukocyte count was 3000/mm³ when she started outpatient treatment at our clinic, which gradually dropped to 1860/mm³ within 6 months of Haloperidol decanoate treatment. During this time, hemoglobin dropped 0.8 points (10.9?g/?dL to 10.1 g/dL), and platelet count decreased from 154,000/mm3 to 140,000/mm3. Within one month of discontinuation of haloperidol decanoate, patient decompensated and was admitted to the psychiatry inpatient unit. Hematology was consulted; lab work to exclude other causes of pancytopenia was completed and haloperidol induced pancytopenia was suspected. She didn't receive any more haloperidol decanoate during her hospital stay. She consistently refused oral medications and became catatonic. Court order for medication-over-objection was obtained but she continued refusing oral medications. As a result, she received Olanzapine 5?mg IM consistently for few days which ultimately resulted in clinical improvement. She was discharged after 2 months of inpatient stay. Her cell counts gradually trended upwards during the inpatient stay. At the time of discharge from the inpatient unit, her WBC count had increased to 5100/mm3, hemoglobin increased to 11.2?g/?dL, and platelet count remained stable at 138000/mm3. It took roughly three months, after stopping the haloperidol decanoate, for the counts to normalize. Conclusions Blood dyscrasias should be suspected in patients treated with antipsychotics. Patients on long acting depot antipsychotics might need longer time to recover from blood dyscrasias due to slow wash-out of depot preparations This research was funded by: Not Applicable