Leukopenia is a known hematological side effect of atypical antipsychotics. We report a case of an antipsychotic-naive patient with schizophrenia who developed leukopenia after a single dose of olanzapine, which worsened during subsequent treatment with risperidone. Normalization of the white blood cell counts occurred within 24 hours of risperidone discontinuation. Possible synergistic mechanisms underlying olanzapine-induced and risperidone-induced leukopenia are discussed. This case highlights the challenges in identifying and managing nonclozapine antipsychotic-induced leukopenia in a susceptible patient.