Signet cell carcinoma of the appendix is the rarest and the most aggressive subtype of appendiceal malignancy, typically presenting with non-specific symptoms. We describe a case of a 62-year-old male with large bowel obstruction, with computed tomography demonstrating dilated large bowels from caecum to proximal sigmoid colon and pneumoperitoneum. Intraoperatively, closed loop obstruction caused by dense adherence of sigmoid colon to caecum was noted, which had resulted in caecal perforation. Histopathology study indicated primary appendiceal malignancy of signet cell morphology with intraperitoneal spread to sigmoid colon. Large bowel obstruction from appendiceal malignancy has rarely been reported and similar presentations have not been described in the existing literature. When left-sided large bowel obstruction is suspected to be caused by a malignant stricture, it is essential to consider transperitoneal spread of appendiceal malignancy as potential aetiology, particularly in the elderly.