This work investigated oxygen diffusion in Ti-20Zr-7.5Mo and Ti-20Zr-10Mo alloys by mechanical spectroscopy measurements. The relaxation parameters of the alloys with the body-centered cubic crystal structure were guided by Arrhenius law and mathematical analyses under the peak ratios. The results showed that the peaks are thermally activated, with the shift of Qp-1 to higher temperatures in tests performed at high frequencies. The activation energy (E) and diffusivity (D) of oxygen in the alloys were obtained using a mathematical treatment of the structures derived from the relaxation time, where was obtained E = 1.06 ± 0.01 eV and D = (5.75 ± 0.63) ×10−10 m2/s for Ti-20Zr-7.5Mo alloy, and E = (0.77 ± 0.04) eV and D = (2.64 ± 0.45) ×10−13 m2/s for Ti-20Zr-10Mo alloy.