Although　Ga　doping　can　weaken　the　electron　phonon　coupling　in　n-type　PbTe,　Ga-doped　PbTe　has　a　relatively　low　carrier　concentration　(n)　and　high　lattice　thermal　conductivity　(κlat),　resulting　in　a　lower　figure　of　merit　(ZT)　compared　with　those　of　other　top-performing　n-type　PbTe-based　thermoelectric　materials.　Herein,　we　report　the　extraordinary　role　of　Zn　in　enhancing　the　thermoelectric　performance　of　Ga-doped　PbTe.　It　is　discovered　that　Zn　can　simultaneously　improve　the　electronic　transport　properties　and　decrease　the　κlat　of　Ga-doped　PbTe,　thereby　affording　a　record　high　ZTavg　∼　1.26　at　400-873　K,　with　a　maximum　ZT　value　of　1.55　at　723　K.　The　isoelectronic　substitution　of　Zn　for　Pb　in　Ga-doped　PbTe　increases　the　electrical　conductivity　and　n　by　inducing　the　nucleation　and　growth　of　Ga2Te3　in　the　second　phase.　The　formation　of　Ga2Te3　results　in　nonstoichiometry　and　Te　deficiency　in　the　PbTe　matrix,　which　increases　the　number　of　electron　carriers.　Additionally,　discordant　Zn　and　Ga　atoms　with　displacing　off-center　from　the　ideal　octahedral　positions,　as　well　as　Ga2Te3　nanocrystals　ranging　from　30　to　200　nm　coherently　embedded　into　the　PbTe　matrix　effectively　weaken　the　phonon　modes　and　scatter　heat-carrying　phonons,　resulting　in　a　significant　reduction　in　κlat.　This　journal　is　©　The　Royal　Society　of　Chemistry.