Ce2MnN3F2-delta has been synthesised via low-temperature fluorination of the ternary nitride Ce2MnN3. To the best of our knowledge, Ce2MnN3F2-delta is the first quaternary nitride-fluoride to be reported. The reaction of Ce2MnN3 with 10% F-2/N-2 at 95-115 degrees C yields the fluorinated phase Ce2MnN3F2-delta, with tetragonal symmetry (P4/nmm a = 3.8554(4) angstrom and c = 13.088(4) angstrom based on neutron powder diffraction), accompanied by starting material. Rietveld refinement supports a staged fluorine insertion reaction (into alternate rocksalt layers) to give a product with stoichiometry Ce2MnN3F2-delta. A comparison with the formation of Sr2TiO3F2 and the isostructural LaSrMnO4F indicates that two F- anions are inserted but no F-/N3- substitution takes place. Magnetic susceptibility measurements show a transition from Pauli paramagnetic behaviour, in Ce2MnN3, to paramagnetic behaviour upon fluorination. The effective magnetic moment in Ce2MnN3F2-delta, mu(eff) = 5.38 mu(B), is consistent with an intermediate value between that of Mn3+ (4.9 mB) and Mn2+ (5.9 mB) supporting the proposed stoichiometry, Ce2MnN3F2-delta.