Background: Dementia screening is an important step for appropriate dementia-related referrals to diagnosis and treat possible dementia. Objective: We sought to estimate the prevalence of no reported dementia-related diagnosis in a nationally representative sample of older Americans with a cognitive impairment consistent with dementia (CICD). Methods: The weighted analytical sample included 6,036,224 Americans aged at least 65 years old that were identified as having a CICD without history of stroke, cancers, neurological conditions, or brain damage who participated in at least one-wave of the 2010–2016 Health and Retirement Study. The adapted Telephone Interview of Cognitive Status assessed cognitive functioning. Those with scores≤6 were considered as having a CICD. Healthcare provider dementia-related diagnosis was self-reported. Age, sex, educational achievement, and race and ethnicity were also self-reported. Results: The overall estimated prevalence of no reported dementia-related diagnosis for older Americans with a CICD was 91.4%(95%confidence interval (CI): 87.7%–94.1%). Persons with a CICD who identified as non-Hispanic black had a high prevalence of no reported dementia-related diagnosis (93.3%; CI: 89.8%–95.6%). The estimated prevalence of no reported dementia-related diagnosis was greater in males with a CICD (99.7%; CI: 99.6%–99.8%) than females (90.2%; CI: 85.6%–93.4%). Moreover, the estimated prevalence of no reported dementia-related diagnosis for non-high school graduates with a CICD was 93.5%(CI: 89.3%–96.1%), but 90.9%(CI: 84.7%–94.7%) for those with at least a high school education. Conclusion: Dementia screening should be encouraged during routine geriatric health assessments. Continued research that evaluates the utility of self-reported dementia-related measures is also warranted.