The carrier concentration of chemically synthesized Bi2Te3-based nanocrystals (NCs) is for the first time reported to be adjusted by forming ternary Bi2−xSbxTe3 NCs (x = 0.02, 0.05, 0.10, 0.20, 0.50, and 1.50) through partial substitution of Bi with Sb. Carrier concentrations of ternary Bi2−xSbxTe3 NCs were successfully adjusted by a factor of more than 10 controlled by the stoichiometric partial Sb/Bi substitution level. The power factors of the stoichiometric ternary Bi2−xSbxTe3 NCs improved three times compared to the parent Bi2Te3 due to the carrier concentration adjustment.