Notably enhanced Mn2+ yellow emission is observed in CsCl modified and Eu2+/Mn2+ codoped GeGaS glasses under near-ultraviolet (NUV) excitation. The plausible efficiency of energy transfer (ET) from Eu2+ to Mn2+ is as high as 91%, which is obtained by measurement of luminescence decay of Eu2+ in samples doped with and without Mn2+. The Eu2+/Mn2+ codoping significantly increases the excitation cross section at the NUV region, which is at heart of the enhanced Mn2+ yellow emission. The ET processes responsible for the enhanced luminescence are discussed.