Multiple types of fistulas associated with the appendix have been reported; however, duodenal fistula resulting from perforated acute appendicitis has only been documented in one previous case. In this report, we present the case of an 18-year-old male patient who was diagnosed to have a complicated appendicitis in its normal position with abscess formation. He was started on IV antibiotics and underwent a CT-guided drainage of the abscess with drain placement. Two days later due to biliary output from the drain, CT fistulography and diagnostic laparoscopy were performed that revealed the presence of a duodenal fistula. The potential for duodenal fistula formation in patients with complicated appendicitis must always be taken into consideration. Consequently, it is crucial to establish an appropriate management plan aimed at preventing additional serious complications arising from duodenal perforation.