Background: It is believed that timely recognition and diagnosis of dementia is a pre-condition for improving care for both older adults with dementia and their informal caregivers. However, diagnosing dementia often occurs late in the disease. This means that a significant number of patients with early symptoms of dementia and their informal caregivers may lack appropriate care. Objectives: To compare the effects of case management and usual care among community-dwelling older adults with early symptoms of dementia and their primary informal caregivers. Design: Randomized controlled trial with measurements at baseline and after 6 and 12 months. Setting: Primary care in West-Friesland, the Netherlands. Participants: 99 pairs of community-dwelling older adults with dementia symptoms (defined as abnormal screening for symptoms of dementia) and their primary informal caregivers. Intervention: 12 months of case management by district nurses for both older adults and informal caregivers versus usual care. Measurements: Primary outcome: informal caregiver's sense of competence. Secondary outcomes: caregiver's quality of life, depressive symptoms, and burden, and patient's quality of life. Process measurements: intervention fidelity and caregiver's satisfaction with the quality of case management. Results: Linear mixed model analyses showed no statistically significant and clinically relevant differences over time between the two groups. The process evaluation revealed that intervention fidelity could have been better. Meanwhile, informal caregivers were satisfied with the quality of case management. Conclusion: This study shows no benefits of case management for older adults with dementia symptoms and their primary informal caregivers. One possible explanation is that case management, which has been recommended among diagnosed dementia patients, may not be beneficial if offered too early. However, on the other hand, it is possible that: (1) case management will be effective in this group if more fully implemented and adapted or aimed at informal caregivers who experience more severe distress and problems; (2) case management is beneficial but that it is not seen in the timeframe studied; (3) case management might have undetected small benefits. This has to be established. Trial registration: ISCRTN83135728. (aut. ref.)