A series of Eu3+-doped KBaY(BO3)2 phosphors was synthesized through a conventional solid-state reaction method. X-ray power diffraction and photoluminescence spectra were used to characterize the phosphors. The KBaY(BO3)2:Eu3+ phosphor showed an intense orange-red emission at 591 nm and red emission at 610 nm under near-UV (392 nm) and blue-light (463 nm) excitation. These results suggest that KBaY(BO3)2:Eu3+ phosphors are suitable for near-UV or blue-light excitation. Compared with Eu3+ single-doped samples, Eu3+ and Bi3+ co-doped samples possess a peak value of 310 nm, which implies the energy transfer between Bi3+ and Eu3+. Moreover, the energy-transfer mechanism between Eu3+ and Bi3+ in KBaY(BO3)2 was explored, and the mechanism was found to be a dipole–quadrupole interaction. The emission peak intensities of the KBaY(BO3)2:Eu3+ phosphor at 591 and 610 nm are significantly enhanced with the co-activator Bi3+ ion.