AbstractPhase equilibrium of Nb–Si–X ternary alloys (X = Zr, Ta, Al) was predicted by thermodynamic calculations. Microstructure characterization and phase identification have been performed to investigate the phase equilibrium and validate the prediction. High-temperature compression tests were performed to evaluate the mechanical properties. All alloys exhibited ssNb, Nb5Si3, and Nb3Si phases. Zr addition increased strength at both room and elevated temperatures. The alloy with large primary silicide islands exhibited a higher 0.2 pct proof stress.