The phase equilibria in the Tl₂Te–Tl₉TbTe₆ system were investigated by using DTA, XRD, SEM-EDS technique and microhardness measurements. The phase diagram of the system as well as concentration dependence of the unit cell parameters and microhardness were constructed. It was established that the system is characterized by formation of the wide fields of solid solutions with Tl₅Te₃-type structure. However, the system is non-quasi-binary due to the peritectic melting of the Tl₉TbTe₆ compound.