Due to the high exothermic characteristic of NiAl during the reaction synthesis process from Ni–Al elemental powders, the NiAl intermetallic melts frequently, and the specimens are difficult to maintain their original shape, which leads to the inhomogeneity of the pore size and morphology. To tackle this problem, porous NiAl intermetallic monolith with controllable shape and pore structure was prepared through thermal explosion (TE) using NaCl as space holder. The TE behavior was recorded, and the effect of the volume fraction of NaCl on the phase composition, macroscopic feature, pore morphology and open porosity were investigated. The results showed that NiAl was the main phase in the products, and the specimen was free from cracking or deforming when NaCl content reached 30 vol%. The interconnected channel and pore windows were formed, and the open porosity was improved greatly to 63% by adding 50 vol% NaCl. The leachable space holder route provides a simple way to control the shape, pore structure and open porosity of the synthesized porous NiAl intermetallic.