Evidence on potentially modifiable risk factors for dementia is accumulating rapidly, including e.g. physical inactivity, hypertension, or diabetes. It is unclear to what extent these risk factors are known among the general population in Germany. We investigated knowledge on risk and protective factors for dementia and openness to eHealth interventions for brain health in the older general population in Germany. A population-based telephone survey among randomly selected community-dwelling adults aged ≥ 60 years was conducted. We assessed sociodemographic factors, knowledge on risk and protective factors for dementia, openness towards eHealth and psychosocial outcomes (health literacy, resilience). Factors associated with interest in information on brain health and openness towards eHealth interventions were assessed using multivariable logistic regression. Of n = 500 respondents (mean age: 74.8 years, % female: 62.8), 67.9% believed that dementia risk is modifiable. Participants mostly endorsed physical and cognitive activity as protective factors and social isolation as a risk factor. Knowledge on cardiovascular risk factors was low to moderate. 38.0% were interested in information on dementia risk reduction. Better knowledge of risk factors for dementia and higher age were linked to interest in information on brain health. Being widowed and higher levels of health literacy were associated with lower interest in information. Openness to eHealth interventions was moderate (46.2%). Younger age, better knowledge of risk and protective factors were linked to openness towards eHealth tools, as was knowing someone with dementia and interest in information on brain health. Belief in preventability of dementia was higher in our sample than previously reported. However, knowledge on cardiovascular risk factors for disease was insufficient and more information and intervention approaches targeted at older adults are needed. Interest in information on dementia risk reduction and eHealth approaches was moderate, and further studies are warranted to assess needs and concerns of older adults regarding dementia prevention.