The phase equilibria in the system Tl₂Se–Tl₂Te–TlSbTe₂–TlSbSe₂ have been studied by DTA and XRD methods. The isothermal section at 300 K, polythermal sections Tl₉SbSe₆–Tl₉SbTe₆ (1), 2Tl₂Se–TlSbTe₂ (2) and 2Tl₂Te–TlSbSe₂ (3) of the phase diagram are constructed. It is shown that the section (1) is a quasi-binary one and forms a continuous series of solid solutions with morphotropic phase transition at the composition ≈15 mol.% Tl₉SbTe₆.  Sections (2) and (3) are non-quasibinary and cross the different phase areas of the reversible mutual system 3Tl₂Se + Sb₂Te₃«3Tl₂Te+Sb₂Se₃.