Background: Acute appendicitis readily comes to mind as a possible diagnosis in any patient presenting with right iliac fossa pain. Thus, a male patient with right sided lower intra-abdominal pain from orchitis, might be diagnosed as having acute appendicitis, especially if the physical examination has been inadequate. Aim: To report a patient thought to have acute appendicitis but who turned out to have an intra-abdominal right orchitis. Case Report: A 26-year-old man presented at His Stripes Hospital, Enugu , with a 3-day history of fever, a right-sided lower abdominal pain, anorexia, nausea and intermittent vomiting. On examination, there was marked tenderness in the right iliac fossa. He was diagnosed as having acute appendicitis. Unfortunately, the external genitalia were not examined. At surgery, his appendix was found to be normal, but an oval shaped solid mass, measuring 2 cm x 2 cm was found lying on the anterior surface of the terminal ileum. The inflamed mass was resected, followed by an incidental appendicectomy. The resected mass turned out to be an inflamed atrophic testis on histological examination. Conclusion: In any male patient with a clinical diagnosis of acute appendicitis, the possibility of a right-sided intraperitoneal orchitis should be excluded by examination of the external genitalia. Keywords: Appendicitis, Intra-peritoneal orchitis, Differential diagnosis, Enugu