The formation of a dispersion of rare-earth metal oxide particles in Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) was studied in order to improve the mechanical properties of TNTZ without increasing its Young's modulus. This dispersion of oxide particles was formed through a reaction between the added rare-earth metal and the oxygen contained in TNTZ. Yttrium or cerium was added to TNTZ for this purpose. Well-dispersed oxide particles are formed, especially in the case of the Y-added TNTZ. Low Young's modulus is retained in both Y- and Ce-added TNTZ. The tensile strength of Y-added TNTZ with a Y concentration of 0.1 mass% improves by 11% as compared to that of TNTZ. The 0.2% proof stress slightly increases in Y- and Ce-added TNTZ for Y concentrations below 0.1 mass% and a Ce concentration of 0.05 mass%.