Understanding the prevalence of beliefs, attitudes, and expectations about Alzheimer's disease dementia in the public could inform strategies to mitigate stigma. Random sample of 317 adults from the U.S. public was analyzed to understand reactions toward a man with mild-stage Alzheimer's disease dementia. In adjusted analyses, over half of respondents expected the person to be discriminated against by employers (55.3%; 95% confidence interval CI = 47.0–65.2) and be excluded from medical decision-making (55.3%; 95% CI = 46.9–65.4). Almost half expected his health insurance would be limited based on data in the medical record (46.6%; 95% CI = 38.0–57.2), a brain imaging result (45.6%, 95% CI = 37.0–56.3), or genetic test result (44.7%; 95% CI = 36.0–55.4). Public education and policies are needed to address concerns about employment and insurance discrimination. Studies are needed to discover how advances in diagnosis and treatment may change Alzheimer's disease stigma.