Ni₃AlC_x was synthesized by two methods, argon arc melting and solid state reaction methods. X-ray diffraction measurements revealed that the samples prepared by the arc-melting method are in a single phase with the Cu₃Au type crystal structure. In x >0.02, all the samples do not show the ferromagnetism but show Pauli paramagnetism while the samples prepared by the solid state reaction method show a tendency of ferromagnetism at about 280 K in the temperature derivative magnetization. From the ²⁷Al NMR measurements, we found the absence of the magnetic phase transition for the samples with x =0.1 prepared by both methods. We conclude that for the samples prepared by the solid state reaction, the enhancement of the magnetization with a tendency of the ferromagnetism is extrinsic, which may be attributed to the possible deposition of Ni-based alloy.