This study was designed to determine whether dietary supplementation with medium-chain triglycerides (MCT) can improve cognitive function in aged dogs by providing the brain with ketones as an alternative energy source. Aged dogs were randomized into two groups based on baseline cognitive tests and were maintained on either a control diet or an MCT diet for eight months. During the feeding trial, dogs were tested on a battery of cognitive test protocols to assess learning ability, memory and attention. Dogs fed the MCT diet showed significantly better performance on most of the cognitive tests than the control dogs