Background <p>Dementia has become a national health priority in Vietnam due to its growing prevalence in the aging population. Although the national dementia strategy highlights health education as a key approach, there is limited formative data on public knowledge. This study aims to assess dementia knowledge among Vietnamese adults and identify factors associated with it.</p> Methods <p>A cross-sectional study was conducted with 967 adults from eight provinces in Vietnam, using a structured questionnaire covering four dementia knowledge domains. Two open-ended questions were included to explore community perspectives. Quantitative data were analyzed using descriptive and multiple linear regression methods, while qualitative responses underwent thematic analysis.</p> Results <p>The participants demonstrate an average level of dementia knowledge, with an overall correct response rate of 50%. While 82.9% correctly recognized memory loss as a primary symptom of dementia, 60.7% mistakenly believed that "dementia is a normal part of aging”. Around 20–30% demonstrated gaps in knowledge related to diagnosis, risk factors, treatment, and care. Greater knowledge was observed among women, older individuals, those with higher monthly income, married people, and those who actively seek information or have familiarity with people with dementia. Our findings revealed public stigma toward people with dementia, but also emphasized social support as a cultural value that could inform the design of culturally appropriate intervention programs.</p> Conclusions <p>The findings highlight the urgent need to raise awareness to address misconceptions and stigma, and guide future interventions by identifying priority groups, adapting global initiatives, and integrating dementia education into existing non-communicable disease programs.</p>