An important approach to understanding RNA-based catalytic function by ribonuclease P is the investigation of its evolutionary diversity in structure and function. Because RNase P enzymes from all organisms are thought to share common ancestry, the fundamental features of structure and biochemistry should be conserved in all of its modern forms. In contrast to the bacterial enzyme, the RNase P enzymes from Eucarya, organelles, and Archaea are poorly understood. This review describes our nascent understanding of the structure and function of RNase P in Archaea, and how this enzyme compares to its homologs in the other evolutionary Domains.