Mitochondrial dysfunction is a key contributor to cognitive impairment, directly affecting neuronal viability, synaptic function, and energy metabolism. In the central nervous system, where energy demand is particularly high, disturbances in mitochondrial dynamics, including impaired oxidative phosphorylation (OxPhos), increased reactive oxygen species (ROS) production, and reduced ATP availability, can compromise synaptic transmission and accelerate cognitive decline. These alterations are commonly observed in neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's (PD), in which mitochondrial dysfunction is closely associated with oxidative stress and neuroinflammatory processes. This review aims to investigate the role of mitochondrial dysfunction in cognitive impairment and the effects of physical exercise as a non-pharmacological strategy to mitigate these alterations. Current evidence indicates that exercise promotes mitochondrial biogenesis through activation of the AMPK/PGC-1α pathway, enhances oxidative metabolism, and improves mitochondrial efficiency. Furthermore, exercise reduces oxidative stress and inflammation while stimulating the release of neurotrophic factors, such as brain-derived neurotrophic factor which support neurogenesis, synaptic plasticity, and neuronal survival. Overall, these findings reinforce the importance of mitochondrial integrity in maintaining cognitive function and highlight physical exercise as a promising strategy to counteract mitochondrial dysfunction and delay the progression of neurodegenerative diseases.