InAs nanowires have been grown by molecular beam epitaxy using Mn as growth catalyst. Nanowires (NWs) have been obtained on SiO2 and oxidized GaAs for growth temperatures in the range of 370–410 °C. The growth temperature is found to be the same as that of the growth of Au-catalyzed InAs wires. These results suggest that the InAs NWs grow with the Mn nanoparticle in the solid phase and allow some comparison with the existing models for Au-catalyzed nanowires. The morphology and the lattice structure were investigated by electron microscopy techniques. The lattice of the wire body is found to be mainly wurtzite InAs. Mn K-edge x-ray absorption fine structure was used to determine the local environment of the Mn atoms: The authors found that most of the Mn atoms are found in a hexagonal MnAs phase.