Combustion synthesis of homogeneous Nb-Ni-Al alloys powder mixtures with nominal compositions Nb10Ni70Al, Nb20Ni65Al and Nb30Ni60Al have been investigated, with emphasis on the reaction mechanisms. Experiments were carried out by thermal explosion mode ("simultaneous combustion") conducted on cylindrical compacts along with differential scanning calorimetry (DSC) analysis of small fragments obtained by crushing the compacts, Microstructural characterization consisted of SEM, EDS and X-ray diffraction analysis, It was found that synthesis occurs as a two-stage reaction. Ni2Al3 and/or NiAl3 are formed in the first stage, with relative amounts depending on the initial compact composition. The first stage reaction can trigger the second stage reaction related to the formation of NbAl3.