Self-healing materials feature the outstanding ability of healing damage inflicted on them. This process leads to the (partial) restoration of the original properties of these materials, in particular of the mechanical properties. Several healing mechanisms involve processes on the nanoscopic level. These lead to the healing of the damage (e.g., crack or scratch) and, as a consequence, the macroscopic mechanical properties are reestablished. Moreover, self-healing of nanomaterials can also be achieved, which is of particular interest, because nanomaterials are particularly prone to damage due to their high surface volume ratio. This review summarizes the involvement of nanoscopic processes in the healing of macroscopic materials, and the healing of nanomaterials is discussed.