Given the reported health benefits of a Mediterranean diet (MedDiet) and delay in cognitive decline, we aimed to determine the level of adherence to a MedDiet using an 11-point scale and examine relationships with cognitive function and psychological well-being. Cross-sectional analyses were undertaken on data from 1183 Australian adults, aged 40-65. Food frequency questionnaires were used to calculate mean intakes of foods included in a MedDiet and foods typically consumed in an Australian diet. Outcome measures included self-reported cognitive failures, memory, anxiety, stress, self-esteem, general health and physical function. The majority of Australians (71.7%) had a medium adherence to a MedDiet pattern. Overall MedDiet adherence was not related to cognitive function. However, intakes of plant foods associated with a MedDiet were positively associated with physical function and general health, and negatively associated with trait anxiety, depression and perceived stress. A substantial proportion of the diet in this Australian sample came from foods not typically consumed in a MedDiet. This is a major limitation when attempting to compare MedDiet adherence in different populations. Global standardisation of serving sizes and food groups are required for adequate comparison. © 2013 Elsevier Ltd.