According to recent surveys, dementia worry (DW) is a widespread phenomenon in mid-life and old age, at least in Western populations. DW has been shown to be only loosely related to sociodemographic factors. Unfortunately, the concept of DW has found only very little conceptual and empirical attention in previous research. In this conceptual review, we take (mostly) a psychological approach to DW. First, we define DW as an emotional response to the perceived threat of developing dementia. We then conceptualise DW as a hybrid, combining elements of ageing anxiety and health anxiety. On the population level, we argue that the high prevalence of DW may be reflective of the increasing awareness of dementia in times of increasing ‘‘dementia encounters’, widespread misperceptions of risks and consequences of dementia and a perceived lack of coping resources. Finally, we propose that DW may affect a range of important behaviours, such as how people interpret evidence of their own or others’ age-related cognitive changes, how they interact with people with dementia, how they anticipate and plan for their future, how they engage in screening and prevention behaviours and how they exploit healthcare resources. We conclude with suggestions for future research, including a further in-depth investigation of psychological and micro-/macrosocial factors associated with DW.