Background The Mediterranean diet has been linked to improved cognitive function and reduced risk of dementia. However, a traditional Mediterranean diet may not meet calcium requirements for older non-Mediterranean populations, which could limit long-term sustainability in Western countries. The current study therefore aimed to determine the cognitive and psychological effects of a Mediterranean diet with adequate calcium for an ageing Australian population. Method: A randomized controlled cross-over design trial compared a Mediterranean diet with 3–4 daily serves of dairy food (MedDairy) with a low-fat (LF) control diet. Forty-one participants aged ≥45 years with systolic blood pressure ≥120 mm Hg and at least two other risk factors for cardiovascular disease completed each dietary intervention for 8 weeks, with an 8-week washout period separating interventions. Attention, processing speed, memory and planning were assessed at the start and end of each intervention using the Cambridge Automated Neuropsychological Test Battery. Mood and health-related quality of life were evaluated using the Profile of Mood States (POMS) and Short-Form Health Survey (SF-36). Dementia risk was also measured using the Framingham Vascular Risk and CAIDE scores. Results Significant improvements were observed for processing speed (P =.04), Total Mood Disturbance (P =.01), Tension (P =.03), Depression (P =.03), Anger (P =.02), and Confusion (P =.004) following the MedDairy intervention. No significant effects were found for attention, memory and planning, or measures of dementia risk. Conclusion Our study provides evidence that a Mediterranean diet supplemented with dairy foods may benefit cognitive function and psychological well-being in an ageing population at risk of dementia.