Neuropsychiatric symptoms are common in Parkinson's disease (PD). We investigated the relationship between neuropsychiatric symptoms and current and future diagnosis of PD dementia (PDD). Individuals with PD who had a study partner were enrolled (n = 696). Study partners were administered the Neuropsychiatric Inventory or Neuropsychiatric Inventory Questionnaire at baseline. Participants were assigned a cognitive diagnosis at baseline and follow up visits. Hallucinations were significantly associated with a diagnosis of PDD cross-sectionally (p < 0.001) and with shortened time to dementia longitudinally among initially nondemented participants (n = 444; p = 0.005). Screening for hallucinations may be useful for assessing risk of dementia in participants with PD.