P-type 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ (0≤x≤7) alloy powders, fabricated by mechanical alloying and melting/grinding processes, were hot pressed and their thermoelectric properties were characterized with the Sb₂Se₃ content and the powder processing method. The Seebeck coefficient and electrical resistivity of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys increased with increasing the Sb₂Se₃ content due to the reduction of the hole concentration. Although the total thermal conductivity of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys decreased with increasing the Sb₂Se₃ content due to the reduction of κ_(el), the lattice thermal conductivity κ_(ph) was not lowered. The figure-of-merit of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys decreased with increasing the Sb₂Se₃ content, because the increment of the electrical resistivity was much larger than the decrement of the thermal conductivity and the increment of the Seebeck coefficient.