Enhancement of the T-4(1g)((4)G)->(6)A(1g)(S-6) red emission of MgGeO3:1% Mn2+ with addition of Yb2O3 is reported. The initial phosphorescence in the Yb2O3 codoped sample is an order of magnitude stronger than that of the Yb2O3-free sample. Thermoluminescence spectra indicate that the introduction of Yb3+ into the host produces traps with a suitable depth, resulting in the enhanced red phosphorescence of Mn2+. The possible mechanism for this phenomenon is explained by a competitive trapping model.