A systematic study of the electrical resistance and thermopower of Bi nanowires has revealed the occurrence of a critical thickness of the wire below which structural defects can strongly influence the charge transport. At low temperatures, in Bi nanowires fabricated by the melt spinning method, the contribution of holes to the thermopower dominates over the electron contribution. Thermoelectric parameters of Bi nanowires may be controlled by applying a thermal treatment and/or a uniaxial pressure. A fairly high value of thermoelectric power factor has been found in a temperature range of 80–300 K, where the mechanism of electron transport is operating in the thermopower.