Phase dependencies in the ternary system Pb3Cl2O2−PbCl2−Pb10(PO4)6Cl2, which is a partial system of the ternary system PbO−P2O5−PbCl2, have been investigated by thermal, X-ray phase, microscopic, dilatometric and IR absorption analyses. The phase diagram of the Pb3Cl2O2−PbCl2−Pb10(PO4)6Cl2 system has been provided. The components have been found not to form any new chemical compounds.