Although a single endosymbiotic event is accepted to have led to the evolution of mitochondria, the machinery that is necessary to import the hundreds of cytosol-synthesized precursor proteins has diverged between various lineages. Plants have the additional requirement to sort protein between mitochondria and plastids, and yet there are also many cases of dual-targeted proteins. The machinery that achieved this process, the mitochondrial protein import apparatus, is composed of a variety of multi-subunit protein complexes on the outer and inner mitochondrial membranes. In plant mitochondria, there are differences in protein composition and/or function in the translocase of the outer membrane and in the intermembrane space. Furthermore, whereas the inner membrane translocases appear more conserved, there is an expansion in the preprotein and amino acid transporter (PRAT) family of proteins that suggest that neofunctionalization has occurred within this family. Our understanding of the processing and degradation of mitochondrial targeting signals in all systems is based on the intensive studies in plants.