A 21-year-old soldier was admitted due to weakness after carrying a heavy military bag and marching for a long time. Neurophysiologic investigation revealed prominent involvement of right brachial plexus and upper cervical root with mild abnormalities of multiple nerves in the other extremities. Hereditary neuropathy with liability to pressure palsy was confirmed by gene test demonstrating deletion of PMP22 gene. This study presents backpack palsy can appear as a first manifestation of hereditary neuropathy with liability to pressure. The possibility of hereditary neuropathy with liability should be strongly considered in a young patient with non-symptomatic multiple neuropathy.