Synaptic plasticity in the adult brain is believed to represent the cellular mechanisms of learning and memory. Mitochondria are involved in the regulation of the complex processes of synaptic plasticity. This paper reviews the current knowledge on the regulatory roles of mitochondria in the function and plasticity of synapses and the implications of mitochondrial dysfunctions in synaptic transmission. First, the importance of mitochondrial distribution and motility for maintenance and strengthening of dendritic spines, but also for new spines/synapses formation is presented. Secondly, the major mitochondrial functions as energy supplier and calcium buffer organelles are considered as possible explanation for their essential and regulatory roles in neuronal plasticity processes. Thirdly, the effects of synaptic potentiation on mitochondrial gene expression are discussed. And finally, the relation between age-related alterations in synaptic plasticity and mitochondrial dysfunctions is considered. It appears that memory loss and neurodegeneration during aging are related to mitochondrial (dys)function. Although, it is clear that mitochondria are essential for synaptic plasticity, further studies are indicated to scrutinize the intracellular and molecular processes that regulate the functions of mitochondria in synaptic plasticity.