DEHPA is prepared through the reaction of phosphorus pentoxide and 2-ethylhexanol:
:4 CHOH  +  PO  →  2 [(CHO)PO(OH)]O
:[(CHO)PO(OH)]O  +  CHOH → (CHO)PO(OH)  +  (CHO)PO(OH)
These reaction produce a mixture of mono-, di-, and trisubstituted phosphates, from which DEHPA can be isolated based on solubility.