The crystal structure of NaMo2P4O14 has been determined from single-crystal X-ray diffraction data. NaMo2P4O14 crystallizes in the triclinic space groupP1- witha = 4.872(1), b = 7.0025(7), c = 8.2620(6)Å, α = 91.468(8), β = 92.53(1), γ = 106.61(1)°,Z = 1, R = 0.020, Rw = 0.029, GOF = 1.192 for 1166 reflections withI > 2.5 σ(I). The structure contains two types of tunnels of which the larger one is occupied by sodium atoms. The framework is built up from MoO6 octahedra and P2O7 groups. It is the first molybdenum phosphate in which equal amounts of isolated Mo3+ and Mo4+ are simultaneously present. A single-phase product can be obtained by heating appropriate amounts of Na2MoO4, MoO2, Mo, and P2O5 in a sealed silica tube at 1100°C.