The densification of titanium diboride (TiB₂) at lower sintering temperature requires the use of sinter-aid. However, from the high temperature application point of view, it is important to assess whether the presence of sinter-aid degrades the material properties, including the oxidation resistance. In the present work, the isothermal oxidation behavior of TiB_2-x wt% MoSi₂ (x=50, 2.5, and 10) composites was carried out using thermogravimetric analyzer in order to study the effect of MoSi₂ content on the oxidation kinetics of TiB₂ at 1200^oC for a duration of 12 h. The oxidized surface of monolithic TiB₂ composed of highly textured rod-like rutile (TiO₂) crystals. In contrast, the oxide scales on TiB2–MoSi2 materials consist of a thin layer of SiO₂ along with TiO₂. Interestingly, the analysis of the continuous measurements of the weight gain reveals parabolic rate law of oxidation for all the investigated ceramics. However, the oxidation kinetics is slower for the TiB₂-10 wt% MoSi₂, probably due to the presence of SiO₂ in the oxide scale