Trimethylphenylammonium bromide is widely used as a phase-transfer catalyst in organic synthesis. It facilitates the transfer of reactants between immiscible phases, enhancing reaction rates and yields in processes such as alkylation, oxidation, and nucleophilic substitution.

In the field of polymer chemistry, it serves as a catalyst or additive in the production of certain polymers, improving their properties and processing efficiency. Additionally, it is employed in the synthesis of specialty chemicals and pharmaceuticals, where its catalytic properties enable the formation of complex molecules.

The compound also finds application in electrochemical studies, particularly in the development of ionic liquids and electrolytes for batteries and supercapacitors, due to its ionic nature and stability. Its role in facilitating efficient chemical reactions and material synthesis makes it a valuable component in various industrial and research applications.