Choline hydroxide (ChOH) is an effective ionic liquid (IL) that enables the straightforward construction of β-phosphonomalonates in basic medium. A variety of compounds, including aromatic/heterocyclic and aliphatic aldehydes (1a–p) were reacted with dicyanomethane (2) and diethyl phosphonate (3) to produce the targeted products in good yields (4a–p). The constructed compounds as well as the IL were characterized using spectral 1H, 13C, and 31P NMR.