Although Eu3+ ion-doped Y2O3 has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and displaying. Here, we show that the emission spectra of Y2O3: Eu3+ red phosphors can be broadened by the doping of Nd3+ ion so that the color rendering capability of Y2O3: Eu3+ was remarkably enhanced. Y2O3: Eu3+ and Y2O3: Eu3+, Nd3+ colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu3+ can be splitted into two ones by the doping of Nd3+ ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd3+ ion, it was determined that the optimal doping concentration of Nd3+ ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd3+ ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified energy diagram suggested that the doped Nd3+ ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to generate intense emission from Eu3+ ion in both of C-2 and S-6 sites, instead of preferable one type of Eu3+ site (C-2 or S-6) in the Nd3+ undoped sample.