In contrast to the stable dinitrogen molecule, white phosphorus (P4) and yellow arsenic (As4) are very reactive allotropic modifications of these two heavier pnictogen elements, which has greatly hampered the study of their properties and applications. Thus, the safe storage and transport of them is imperative. Supramolecular caged structures are one of the most efficient approaches for the encapsulation and stabilization of reactive species; however, their use in the P4 and As4 chemistry is very rare. In the current work, we demonstrate a new design strategy for constructing finite cages and including guests based on anion coordination chemistry. The phosphate-coordination-based tetrahedral cages can readily accommodate the tetrahedral guests P4 and As4, which is facilitated by the shape and size complementarity as well as favorable σ-π and lone-pair-π interactions. Moreover, the latter case represents the first example of As4 inclusion in a well-defined tetrahedral cage.