We report a detailed calorimetric study concerning the influence of Yb2O3 and Er2O3 on the non-isothermal crystallization in phosphosilicate melts. The results show that Yb3+/Er3+ ions promote the Zn2SiO4 crystal formation, but suppress the Na3PO4 and AlPO4 formation during cooling. The non-isothermal melt-crystallization kinetics can be well described by the Avrami model. The activation energy Ee of crystallization in both the undoped and Yb3+/Er3+ codoped samples during cooling is determined using the differential iso-conversional method of Friedman. The Ee value decreases with crystallinity (θ = 0.1 to 0.9) during cooling for both glasses, and introducing Yb2O3 and Er2O3 leads to an increase in energy barrier of crystallization upon cooling.