Background: With the rise in the aging population and absence of a cure for dementia, cost-effective prevention strategies for those 'at risk' of dementia including those with depression and/or mild cognitive impairment are urgently required. Objective: This study evaluated the efficacy of a multifaceted Healthy Brain Ageing Cognitive Training (HBA-CT) program for older adults 'at risk' of dementia. Methods: Using a single-blinded design, 64 participants (mean age = 66.5 years, SD = 8.6) were randomized to an immediate treatment (HBA-CT) or treatment-as-usual control arm. The HBA-CT intervention was conducted twice-weekly for seven weeks and comprised group-based psychoeducation about cognitive strategies and modifiable lifestyle factors pertaining to healthy brain aging, and computerized cognitive training. Results: In comparison to the treatment-as-usual control arm, the HBA-CT program was associated with improvements in verbal memory (p = 0.03), self-reported memory (p = 0.03), mood (p = 0.01), and sleep (p = 0.01). While the improvements in memory (p = 0.03) and sleep (p = 0.02) remained after controlling for improvements in mood, only a trend in verbal memory improvement was apparent after controlling for sleep. Conclusion: The HBA-CT program improves cognitive, mood, and sleep functions in older adults 'at risk' of dementia, and therefore offers promise as a secondary prevention strategy.