Nicolau syndrome (livedoid dermatitis) is a very rare complication of intramuscular injections and manifests as excruciating pain immediately after injection. We describe a 3-year-old boy with diagnosis of Nicolau syndrome after intramuscular benzathine penicillin injection to the midanterior part of the left thigh. He was treated with hyberbaric oxygen and pentoxyphilline in addition to supportive treatment and recovered with no sequelae.