ABSTRACT Primary signet-ring cell carcinoma (SRCC) of vermiform appendix is extremely rare. A 62-year-old man presented to the Surgical Clinics with right lower abdominal pain, where he was diagnosed with acute appendicitis based on the history and examination with hematologic investigations and computed tomography. Appendectomy specimen grossly showed acute inflammation with appendiceal adhesions and body of the appendix showed wall thickening and luminal occlusion. Microscopically nests of carcinoma cells were seen with compressed nuclei and intracytoplasmic mucin invading into the muscular layer. No lymphovascular permeation was seen. The cut margins were negative for carcinoma cells. Immunohistochemically, SRCC cells were positive for cytokeratin (CK) AE1/3, EMA, CEA, MUC2, and high Ki-67 labeling index. They were negative for CK5/6, CK7, Vimentin, MUC1 and chromogranin. Our patient is fine after 6 months of follow up, with no evidence of recurrence or metastasis.