NH4[PO2F(NH2)] has been prepared by the reaction of a betaine py·PO2F with excess ammonia in acetonitrile solution, while the ammonolysis of DMAP·PO2F with a stoichiometric amount of NH3 yields [DMAPH][PO2F(NH2)]. The crystal structure of the latter was determined by single‐crystal X‐ray diffraction, which revealed that the anions [PO2F(NH2)]— are linked to infinite chains by double N—H···O bridges. Additional strong N—H···O bridging bonds connect each anion with its [DMAPH]+ counterion. The formation of a new betaine NH3·PO2F in the solution of py·PO2F in liquid ammonia was proved by 31P NMR spectroscopy and by identification of its hydrolysis products.