Trimethylamine is used as a basic catalyst, in the preparation of quaternary ammonium hydroxides and salts, and ion-exchange resins. It is also an important starting material for manufacturing the essential nutrient choline; conversely, excessive choline intake results in its degradation to TMA in the body.

Organic synthesis, especially of choline salts, warning agents for natural gas, manufacture of disinfectants, flotation agents, insect attractants, quaternary ammonium compounds, and plastics.