OBJECTIVES: Evaluate the effect of a health promotion campaign aimed at increasing awareness about dementia risk reduction in middle-aged community-dwelling individuals in the Netherlands. DESIGN: A 10-month public health campaign using mass media and community participation, supported by eHealth. Population-level difference in awareness before and after the campaign, including variation between demographic groups, was assessed in two independent cross-sectional samples from the same target population. SETTING: The public health campaign was launched in the Province of Limburg, the Netherlands, targeting all inhabitants aged 40-75 years old. Three specific districts within the Province were chosen for an additional community participation approach, in which local stakeholders were invited to support the campaign. RESULTS: No pre- (n=590) post- (n=602) difference was observed in people agreeing to the statement that dementia risk reduction is possible (X(1)=1.27, p=0.260). For the individual lifestyle factors, physical activity (7.6% increase (X(1)=7.48, p=0.006)) and healthy diet (10.5% increase (X(1)=12.37, p≤0.001)) were identified more often as being protective against dementia after the campaign. Of all risk/protective factors assessed, cognitive activity was identified most often at both preassessment (79.4%) and postassessment (80.4%), but there was no increase in awareness (X(1)=0.17, p=0.677). Self-reported exposure to the campaign was associated with greater awareness and motivation for behavioural change (X(1)=6.52, p=0.011). Compared with mass media only, the addition of community participation resulted in better recognition of campaign material and the eHealth platform. CONCLUSIONS: This study was not able to reach a population-level increase of awareness of dementia risk reduction. Two out of the three lifestyle factors that formed the foundation of the campaign were identified more often after the campaign. Those reported having been exposed to the campaign were more aware and more inclined towards behavioural change.