The influence of spark plasma sintering (SPS) conditions on the optical and mechanical properties of MgAl₂O₄ spinel was investigated for application to infrared windows as parts of military systems. The thermal conditions of SPS, including the temperature and heating rate, have a significant impact on optical and mechanical properties. This study shows that the formation and growth of abnormal grains cause mechanical degradation with an increasing SPS temperature. In-line transmittance (Tin) was affected by the heating rate due to changes in oxygen vacancy and carbon contamination in SPSed samples. The fabricated spinel exhibited excellent flexural strength of 401 MPa and an average mid-infrared transmittance of 84.8% in the range of 3-5 μm.