Alzheimer's disease (AD) is a major health concern as the world population ages. Yet, few studies have examined what the public over the age of 50 knows about AD. This qualitative study, based on 40 in-depth interviews, examines the knowledge of AD by Flemish people between 50 and 80 years old and their cross-source engagement with information sources. Building on AD media representations and theories on media complementarity and health information behaviour, we find that respondents mostly encounter AD information non-purposively via traditional mass media and interpersonal communication, while the internet is occasionally used to purposefully seek information. Novels, personal experiences/social proximity, public figures and particularly film stand out as channels and sources of AD information, suggesting that fictional narratives, personal experiences and being able to identify with others leave lasting impressions and help to communicate and disperse AD information. However, common misconceptions and gaps in knowledge persist, including AD being considered part of the normal ageing process and old age as well as confusing AD with Parkinson's disease. The biomedical perspective and the tragedy discourse prevail among the majority of respondents, who describe AD in terms of decline, loss and death and as ‘the beginning of the end’. Only a few, typically female respondents, appear aware of the role of individual health behaviour and lifestyle choices to prevent dementia or delay its onset. The misconceptions of AD and gaps in knowledge, as well as the fact that a third of all cases of dementia might be delayed or prevented by managing lifestyle and other risk factors, stress the importance of public educational programmes and the need to emphasise and raise awareness of preventative behaviour. Overall, the findings from this study can be of help to public health communicators and dementia-awareness campaigns, as well as AD training programmes for health-care professionals and family care-givers.