This study aims at studying the microstructure and mechanical properties of nanocrystalline Ni3Al-xB (0.0<x<1.5 at%) alloy, made by mechanical alloying (MA) and spark plasma sintering (SPS). Effects of milling time as well as boron addition on the crystallite size, lattice strain, and powder morphologies of synthesized powders were studied using scanning electron microscope (SEM) and X-ray diffractometer (XRD). Synthesized powders were consolidated under uniaxial compression 50 MPa at 950 °C for 10 min. Shear punch and hardness tests were used to evaluate mechanical properties of consolidated specimens. Results show that Ni3Al compound were synthesized after 30 h of milling in a planetary ball mill with the rotation speed of 350 rpm and ball-to-powder ratio 10:1. Synthesized powders have crystallite size in the range 15–20 nm depending on the milling time. Results also show that boron addition is influential the most when boron content is between 0.5–1.0 at%. Boron addition is accompanied with a significant improvement of hardness and shear strength and a drop in the ductility of Ni3Al-xB (0.0<x<1.5 at%) alloy. The details concerning structure-properties relationship in this system are discussed in this paper.@en