Mn ions were co-doped in yttrium aluminum garnet doped cerium (YAG:Ce) phosphors as a co-activator and host lattice element using the co-precipitation method. These ions broadened the emission spectra of the pure YAG:Ce phosphor, which is caused by the 2E-4A2, 5E-5T2 or 1T2-5T2 transition. From our X-ray diffraction results, we observed that Ce3+ (1.032 Å) was substituted at the Y3+ (0.900 Å) site, and Mn4+ (0.538 Å) and Mn3+ (0.67 Å) were substituted at the Al3+ (0.535 Å) site. The chromaticity color co-ordinates of YAG:Ce0.06 is (0.203, 0.167), and the indices of YAG:Ce0.06, Mn0.04 and YAG:Ce0.06, Mn0.08 are (0.249, 0.181) and (0.233, 0.194), respectively. The manganese co-doped yttrium aluminum garnet doped cerium blended with the YAG:Ce phosphor showed improved white light emission.