Understanding ferromagnetism and thermoelectric behavior are crucial in spintronics and thermoelectric device applications. Using density functional theory-based WIEN2k code, we have examined the physical properties of vanadium-based MgV2S/Se4 spinels. The calculated negative formation energies and positive phonon frequency indicate the stability of the studied system. The lowest energy ground state has been predicted to be a ferromagnetic phase. The calculated electronic band structure and density of states show that these materials are half-metallic ferromagnetic. The existence of the ferromagnetic phase is described using the pd hybridization, double exchange interaction model by computing the exchange energy and constants. In addition, the quantum coupling of electrons is caused by the shift of the magnetic moment from the V site to non-magnetic sites (S/Se, Mg). Finally, electronic transport parameters like the Seebeck coefficient, electric and thermal conductivity, and power factor are also determined.