Tetanus is a rare disease in industrialized countries, largely due to the highly protective effect of immunization. We present a case of tetanus in a formerly preterm infant with myelomeningocele repaired in utero, who presented at 44 days of age with poor feeding, lethargy, and increased tone. His symptoms progressed despite a course of antibiotics for presumed meningitis. At 73 days of age (on 29th day of hospitalization), a clinical diagnosis of tetanus was made based on the presence of risus sardonicus, trismus, and generalized hypertonicity. Consequently, tetanus immune globulin, muscle relaxants, and metronidazole were administered. Five months later, the infant has had complete resolution of the hypertonicity, has regained normal jaw movement and swallowing, and is regaining oral feeding skills. This case involved a delay in diagnosis despite clinical symptoms and signs classic, in retrospect, for tetanus, highlighting the importance of recognizing the constellation of symptoms that should lead us to consider this rare diagnosis.