Aim: The authors’ objective is to review how often the appendix is involved in Chinese women undergoing appendectomy at the time of surgery for a mucinous borderline ovarian tumour (mBOT) or invasive mucinous ovarian tumour (IMOT), and to evaluate whether appendectomy is necessary. Materials and Methods: A retrospective study was performed in Queen Elizabeth Hospital in Hong Kong between 2010 and 2016. Women who underwent surgery and whose final diagnosis was mBOT, invasive mucinous ovarian tumour (IMOT) or mucinous appendiceal tumour were included. Results: A total of 78 cases of mucinous borderline or invasive ovarian tumour and appendiceal tumour were identified, of which 75 (96.2%) patients underwent an appendectomy at the time of primary surgery. Forty-six (58%) patients were finally diagnosed with borderline ovarian tumours and 32 (41%) with malignant mucinous tumours. Among the 46 borderline tumours, 4 (9.3%) appendices were grossly abnormal, but none of them were confirmed as malignant. As for those with malignant mucinous disease, 5 of the 32 (15.6%) appendices were visually abnormal, and three were confirmed to be primary mucinous appendiceal tumours. Based on these results, sensitivity, specificity, positive predictive value, and negative predictive value of the macroscopic appearance of the appendix were 100%, 91.7%, 33.3%, 100%, respectively. Conclusion: Primary or metastatic appendiceal neoplasm is not expected in case of the appendix is grossly normal during surgery for a mucinous ovarian tumour with borderline or malignant features. Appendectomy must be performed if the macroscopic appearance of the appendix is abnormal or when pseudomyxoma peritonei (PMP) is present.