Electrical transport and thermoelectric properties of thin indium arsenide nanowires have been investigated in the temperature range between 100 K and 365 K. Charge carrier concentration was varied by a back-gate electrode. In nanowires with a diameter of 20 nm, discrete conductance plateaus are observed at low temperature indicating one-dimensional quantization of the density of states. A mean free path of 135 nm is extracted. At room temperature, the one-dimensional nature leads to drastically enhanced thermoelectric properties. A 100 % increase of the thermoelectric power factor σS2 (calculated from the electrical conductivity σ and the Seebeck coefficient S) is obtained in the nanowires compared to bulk InAs bulk material.