Background Long-acting injectable medications have become an important tool in the treatment of schizophrenia and schizoaffective disorder due to the high rates of medication nonadherence. Olanzapine long-acting injection (OLAI) is a useful therapeutic option for patients who have good tolerability and efficacy to oral olanzapine. Postinjection delirium/sedation syndrome (PDSS) is a rare but potentially serious event with the proposed mechanism of inadvertent intravascular injection of OLAI. This concern necessitates the requirement of a 3-hour monitoring period postinjection. Based on a literature review, there are no clearly defined risk factors for developing PDSS. Case Report A case is presented that describes PDSS in a transgender man undergoing hormone therapy with testosterone. The patient received OLAI for more than 3 years and developed PDSS 9 months after the initiation of injectable testosterone. Discussion There are published case reports of PDSS with the use of OLAI; however, there are no documented cases in a patient undergoing concurrent testosterone therapy. The effect that testosterone has on the vascular system and how it may alter the pharmacokinetics of OLAI has not been studied. Conclusion Despite proper injection technique, PDSS can occur after injection with OLAI. Further research is necessary to identify specific risk factors for the development of PDSS, including the potential effect that hormone therapy may have.