Brain is a vital organ that always has high oxygen demands and is highly vulnerable to injury caused by reactive oxygen species (ROS). The hippocampus is a complex structure seen deep in the temporal lobe which is constituted by the dentate gyrus, hippocampus proper (Cornu Ammonis- CA1-CA4) and subiculum. The important functions of the hippocampus are learning and memory. Age-influenced pathological lesions in the hippocampus and variation in the number of neurons in the hilus are the main discussion of this study. The major gross lesions observed in the brain of both younger and older dogs were cerebral congestion, thickened meninges and cerebral edema. The major histopathological findings in the hippocampus were thickened blood vessels, accumulation of lipofuscin pigments in the neuronal cytoplasm, satellitosis, gliosis, neurons with the vesicular nucleus, chromatolysis and neuronophagia. A statistically significant reduction in the number of neurons in the hilar region of the hippocampus was observed in aged dogs.