In this paper, we report a significant improvement in mechanical and oxidation properties of near eutectic Nb–Si alloys by the addition of aluminum (Al) and control of microstructural length scale. A comparative study of two alloys Nb-18.79at%Si and Nb-12.3at%Si-9at%Al were carried out. The processing for microstructure refinements were carried out by vacuum suction casting in water cooled thick copper mould. It is shown that addition of Al suppresses Nb 3 Si phase and promotes βNb 5 Si 3 phase under nonequilibrium solidification condition. The microstructural length scale and in particular eutectic spacing reduces significantly to 50–100nm in suction cast ternary alloy. A detailed TEM study shows the presence of δ-Nb 11 Si 4 phase in Nb matrix. The hardness of Nb solid solution can be increased as a consequence to a level observed in Nb 3 Si intermetallic due to the well oriented precipitates. Compression test yields the ultimate strength of 1.8±0.1GPa and engineering strain of 2.3±0.03%. In comparison, the binary Nb-18.79at% Si alloy possesses an ultimate strength of 1.35±0.1GPa and strain of 0.2±0.01% when processed under identical conditions. The latter exhibits coarser microstructural length scale (300–400nm) and a brittle behavior. The indentation fracture toughness of Al containing suction cast alloy shows a value of 20.2±0.5MPa√m which represents a major improvement over bulk Nb–Si eutectic alloy. The detailed thermal studies confirm a multifold improvement in oxidation resistance up to 1000°C.