The aim of this review is to present the current state of our understanding on the structure, regulation, and function of plant pathogenesis-related protein family 10 (PR-10). This protein family consists of relatively diverse members subgrouped into classes that suggest different functions. It is believed that PR-10 proteins are involved in plant defense because their genes are usually induced upon the attack of various pathogens and by environmental stresses. However, updated evidence shows that PR-10 proteins display several additional functions, including a role in developmental processes and enzymatic activities in secondary metabolism. Because of the complexity of the PR-10 gene family and its potential multiple functions, it is important to summarize current knowledge as basis for a further dissection of the functions of PR-10 proteins and a better understanding of their structural adaptation. This paper provides the first review of existing knowledge of plant PR-10 proteins and examines their structural and functional adaptations.