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We report herein a theoretical study of the high-pressure compressibility of Cd₃V₂O₈, Zn₃V₂O₈, Mg₃V₂O₈, and Ni₃V₂O₈. For Cd₃V₂O₈, we also present a study of its structural stability. Computer simulations were performed by means of first-principles methods using the CRYSTAL program. In Cd₃V₂O₈, we found a previously unreported polymorph which is thermodynamically more stable than the already known polymorph. We also determined the compressibility of all compounds and evaluated the different contributions of polyhedral units to compressibility. We found that the studied vanadates have an anisotropic response to compression and that the change in volume is basically determined by the compressibility of the divalent-cation coordination polyhedra. A systematic discussion of the bulk modulus of M₃V₂O₈ orthovanadates will also be included.