Tris(4-methylphenyl)phosphine oxide is primarily used as a ligand in various catalytic processes, particularly in organic synthesis and polymerization reactions. Its ability to stabilize metal complexes makes it valuable in homogeneous catalysis, where it enhances the efficiency and selectivity of reactions such as cross-coupling and hydrogenation.

In material science, it serves as an additive in the production of advanced polymers and resins, improving their thermal stability and mechanical properties. Additionally, it is employed in the development of organic light-emitting diodes (OLEDs) and other optoelectronic devices, where it contributes to the optimization of charge transport and emission characteristics.

Its role in coordination chemistry also extends to the synthesis of organometallic compounds, which are essential in pharmaceuticals and agrochemicals. Overall, it is a versatile compound with significant applications in catalysis, materials science, and electronics.