Osteomyelitis is rare in the neonatal period. Many etiologic factors for causing neonatal osteomyelitis have been discussed in the literature; however, premature rupture of the membranes has never been emphasized. We report on a neonate with osteomyelitis of the right humerus infected with an uncommon pathogen, Klebsiella pneumonia. In the absence of any perinatal disease, premature rupture of the membranes was suggested to be the cause of the illness. The infant was initially regarded as having Erb palsy because of the absence of systemic symptoms and lack of perinatal high-risk factors. Antibiotic administration was delayed for 3 weeks. Luckily, nearly complete recovery was noted after 2 months of follow up. We emphasize the importance of considering osteomyelitis in a newborn infant with limb palsy, particularly in the presence of premature rupture of the membranes of the mother. We also discuss the results of the microbial examination and significance of magnetic resonance imaging in neonatal osteomyelitis.