Diethyl phosphite is reported to be chemical warfare agent (CWA) simulant, simulant for nerve agents sarin, soman, tabun, and VX.

Diethyl phosphite may be used to prepare the nickel chloride-diethyl phosphite system, efficient catalyst for the cross-coupling reaction between various functionalized arylzinc halides and aryl bromides, triflates and activated chlorides. It may be used:

• in the stereoselective synthesis of β-fluorinated alkylphosphonates
• in the synthesis of homoallylic bromide
• in the synthesis of series of carbazole-based α-aminophosphonates