The thermoelectric properties of Ge-doped Bi0.4Sb1.6−xGexTe3 (x = 0, 0.01, 0.015, 0.02) were investigated in the temperature range from 300 K to 525 K. The results show that Ge doping brings about 13–52% increase in electrical conductivity due to the increase of hole concentration, and 5–11% decrease in thermal conductivity owing to enhanced phonon scattering by the dopant atoms. As a result, a maximum thermoelectric figure of merit (ZT) reaches 1.48 at 350 K for Bi0.4Sb1.59Ge0.01Te3, which is ~25% larger than that of Bi0.4Sb1.6Te3. Present results demonstrate that Ge doping is an effective way to enhance the thermoelectric performance of Bi0.4Sb1.6Te3 alloy.