Erysipelothrix rhusiopathiae is a Gram-positive bacillus that causes infections primarily in animals. In humans, the bacteria usually cause localized or generalized cutaneous infections. A 75-year-old man with chronic alcoholism presented with abdominal pain. Abdominal computed tomography and laboratory findings suggested an intra-abdominal abscess in the periaortic soft tissue. While no definitive infectious source was identified, E. rhusiopathiae was identified by 16S rRNA-based gene sequencing from culture-negative, periaortic necrotic tissue, subsequent to empiric antibiotic treatment. It is suggested that E. rhusiopathiae has the potential to cause intra-abdominal abscesses. This case report highlights the usefulness of DNA sequencing to identify pathogens in patients pretreated with antibiotics.