In eukaryotes, mitochondria are required for the proper function of the cell and as such the maintenance of proteins within this organelle is crucial. One class of proteins, collectively known as the AAA+ (ATPases associated with various cellular activities) superfamily, make a number of important contributions to mitochondrial protein homeostasis. In this organelle, they contribute to the maturation and activation of proteins, general protein quality control, respiratory chain complex assembly, and mitochondrial DNA maintenance and integrity. To achieve such diverse functions this group of ATP-dependent unfoldases utilize the energy from ATP hydrolysis to modulate the structure of proteins via unique domains and (or) associated functional components. In this review, we describe the current status of knowledge regarding the known mitochondrial AAA+ proteins and their role in this organelle.