The formation of organic functionalization layers on germanium (Ge) nanowires was investigated using a new synthetic protocol employing arenediazonium salts. Oxide-free, H-terminated Ge nanowires were immersed in diazonium salt/acetonitrile solutions and the molecular interface of the functionalized nanowires was analyzed by reflectance infrared spectroscopy and X-ray photoelectron spectroscopy. The morphology of the modified nanowires was investigated by electron microscopy. Surface functionalization of the nanowires was found to be slow at room temperature, but proceeded efficiently with moderate heating (50 °C). The use of arenediazonium salts can result in the formation of aryl multilayers, however the thickness and uniformity of the organic layer was found to be strongly influenced by the nature of the substituents on the aromatic ring. Substituents attached to the 3-, 4-, and 5-ring positions hindered the formation of multilayers, while the presence of sterically bulky ring substituents affected the homogeneity of the organic layers. We successfully demonstrate that arenediazonium salts are very flexible precursors for nanowire functionalization, with the possibility to covalently attach a wide variety of aromatic ligands, offering the potential to alter the thickness of the resulting outer organic shell.Keywords: Nanomaterials; Semiconductors; Surface and Interfacial Phenomena