Surgery always runs the risk of damaging nearby structures. There are no reliable data available on the incidence of iatrogenic nerve damage of the upper extremities. Typical patterns of injuries of the spinal accessory nerve, brachial plexus, axillary nerve, radial nerve, median nerve and ulnar nerve show clear differences in the type of surgery, prognosis under conservative treatment and delay between injury and diagnosis; therefore, in this article the results are presented according to the anatomical structures damaged. Uncertainty in the anatomical preparation and lack of anatomical knowledge are the main reasons for iatrogenic nerve lesions, in addition to a lack of visibility of nerves lying hidden behind bones and joints to be operated on and nerves distant from the actual site of repaired fragments, implants or sutures, which cannot be avoided. The differential diagnostics of iatrogenic nerve lesions appears to be difficult. A delay of several months until a definitive diagnosis is common and impairs the outcome in cases where microsurgical reconstruction becomes necessary. Timely diagnostics carried out directly following the suspicion of iatrogenic nerve lesions by imaging, such as ultrasound and magnetic resonance imaging in combination with electrophysiology are necessary. The indications for a surgical revision should at least be liberally considered. © 2015, Springer-Verlag Berlin Heidelberg.