Patients with Parkinson's disease (PD) sometimes experience symptoms affecting their movement, such as slowness, tremor, stiffness, and balance or walking problems. Many patients also have other symptoms not related to movement, called non-motor symptoms, which may affect one's mood or emotions, memory or thinking, or cause one to see or hear things that aren't real (hallucinations) or believe things that aren't true (delusions). Hallucinations or delusions, together called psychosis, occur in up to 60% of PD patients at some point in time. Parkinson's disease psychosis can sometimes be associated with decreased quality of life, increased nursing home placement, increased rate of death, and greater caregiver burden. There are approximately 50,000 Veterans with Parkinson's disease receiving care in the VA, and up to 30,000 (60%) of them will experience psychosis at some point in time. Quetiapine is an antipsychotic drug approved by the Food and Drug Administration (FDA) that is the most commonly used medication to treat PD psychosis, but more studies are needed to determine if it works for this condition and is also well tolerated and safe. Pimavanserin is a newer antipsychotic drug approved by the Food and Drug Administration (FDA) specifically to treat PD psychosis, but more studies are needed to determine if it works and its safety. The purpose of this research is to gather additional information on the safety and effectiveness of both Quetiapine and Pimavanserin. By doing this study, the investigators hope to learn which of these medications is the most effective course of treatment for people with PD psychosis. Enrollment is open to Veterans nationwide, see your VA provider about the possibility of being referred to one of the study's Hub sites. This can be done through contact from your provider to the study's NSC (Tamara Boney at 267-303-9829).