Single crystals of JEM-phase NdSi(6-z)Al(1+z)O(z)N(10-z) were successfully prepared from starting powders of Si₃N₄, AlN and Nd₂O₃ at 1700 °C for 3 h under nitrogen atmosphere. The z value of Nd-doped JEM-phase was determined to be 0.4 via determination of oxygen and nitrogen by elemental analysis. This result may be beneficial for overcoming the difficulty on preparation of single-phase JEM-phase Sialon materials and further characterization on their properties. The detailed crystal structure of Nd-Sialon was solved on the basis of single-crystal X-ray diffraction data for the first time. The space group is Pbcn (no. 60); a = 9.3060(6) Å, b = 9.7224(6) Å, c = 8.8777(5) Å; Z = 4; V = 803.22(8) ų; D(c) = 3.971 g cm⁻³; R₁ = 0.0297 and wR₂ = 0.0739 for all reflections refined against F², with GooF value of 1.031.