The phonon behavior in incipient ferroelectric (Ni1/3Nb2/3)xTi1−xO2 ceramic solid solutions is investigated with combined Raman, Fourier transformed infrared (FTIR), and dielectric spectroscopy. The (Ni+Nb) incorporation into rutile TiO2 leads to the Raman and infrared modes broadening, the Gaussian‐type Raman peak of A2u(LO) mode, and the dielectric constant (at 14 K) of different compositions being proportional to the mole ratio of Ti cations. It suggests that, with increasing (Ni + Nb)‐substitution, the cationic disorder gradually develops and the disorder‐induced phonon localization occurs. In particular, the soft A2u mode appears to be localized to Ti‐containing regions. This work demonstrates that the combined Raman, FTIR, and dielectric analysis can effectively probe the cationic disorder and phonon localization behaviors in incipient ferroelectric (Ni1/3Nb2/3)xTi1−xO2 and provides an experimental evidence of phonon localization in 3D disordered systems with mass and spring constant disorder, which enriches the understanding of the Anderson localization in vibrational systems.