Metallocarboxypeptidases (MCPs) of the M14 family are Zn2+-dependent exoproteases present in almost every tissue or fluid in mammals. These enzymes perform a large variety of physiological functions and are involved in several pathologies, such as pancreatic diseases, inflammation, fibrinolysis, and cancer. Here, we describe the synthesis and functional/structural characterization of a series of reversible tight-binding phosphinic pseudopeptide inhibitors that show high specificity and potency toward these proteases. Characterization of their inhibitory potential against a large variety of MCPs, combined with high-resolution crystal structures of three selected candidates in complex with human carboxypeptidase A (CPA)1, allowed to decipher the structural determinants governing selectivity for type-A of the M14A MCP family. Further, the phosphinic pseudopeptide framework was exploited to generate an optical probe selectively targeting human CPAs. The phosphinic pseudopeptides presented here constitute the first example of chemical probes useful to selectively report on type-A MCPs activity in complex media.