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The structure-property relationships of the arc melted cast ternary Nb-Si-Mo alloys with hyper-eutectic Nb-19Si-5Mo (A) and Nb-18Si-26Mo (B), as well as hypoeutectic Nb-13Si-4Mo (C) and Nb-12Si-15Mo (D) compositions, have been studied. The influence of Mo concentration on the microstructure, mechanical properties and oxidation behaviour of the investigated ternary Nb-Si-Mo alloys has been examined. Studies on microstructures have been carried out using X-ray diffraction as well as optical, scanning, and transmission electron microscopy along with energy dispersive spectroscopy and image analysis. The microstructures of the alloys A and B contain primary α-(Nb,Mo)5Si3 with a large volume fraction of the eutectic, comprising mixtures of secondary Nbss and α-(Nb,Mo)5Si3. In contrast, microstructures of the alloys C and D exhibit primary Nbss and lower volume fraction of the eutectic. The absence of Nb3Si in the investigated Nb-Si-Mo alloys, and its presence in the cast Nb-Si alloys, suggests that presence of Mo alters the solidification behaviour of the former. Alloying with Mo also increases the volume fraction of coarse secondary Nbss in the non-lamellar eutectic, and decreases the interlamellar spacing in the lamellar eutectic. The lattice parameter of bcc-Nbss decreases with increasing concentration of Mo. In case of the tetragonal structured α-(Nb,Mo)5Si3, the value of ‘c’ increases, while that of ‘a’ decreases with increasing Mo content, resulting in increase of the c/a ratio.