Magnetic spinel oxides LiZ2O4 (Z = Mn, Fe, Co, and Ni) have recently appealed the scientific community due to their interesting magnetic and thermoelectric applications. In the current article, the electronic, magnetic, and thermoelectric properties of LZO have been elaborated using density functional theory-based Wien2k code. The band structures and total density of states ensure the half metallic ferromagnetic (HMF) nature of the studied compounds. Furthermore, the magnetism is discussed in detail using crystal field, John-Teller, and exchange energies involved in the system and spin density. Finally, electrical conductivity, thermal conductivity, power factor, Seebeck coefficient, and thermal efficiency computed by using BoltztraP code suggest these compounds for thermoelectric device fabrications.