Ethyltributylphosphonium 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 nucleophilic substitutions, oxidations, and polymerizations.

In the field of material science, it serves as an ionic liquid precursor, contributing to the development of electrolytes for batteries and other electrochemical applications due to its stability and ionic conductivity.

Additionally, it is employed in the synthesis of specialty chemicals and pharmaceuticals, where its catalytic properties enable efficient and selective transformations. Its role in green chemistry is also notable, as it can reduce the need for hazardous solvents and improve the sustainability of chemical processes.