Abstract Objective This study aims to determine whether long-term follow-up is required following fertility sparing surgery (FSS) for mucinous borderline ovarian tumours (MBOT). Design Retrospective cohort study. Setting Tertiary gynaecology oncology centre at Queen Charlotte’s and Chelsea Hospital, Imperial College Healthcare NHS Trust (United Kingdom). Population or sample Patients under follow-up post-surgery for MBOT in the ovarian clinic from 2007-2025. Methods Rate of recurrence was compared amongst patients who underwent primary debulking, unilateral salpingo-oophorectomy (USO) or ovarian cystectomy for MBOT. Main outcome measures Duration of follow-up, rate of disease recurrence and the requirement for further surgery. Results Out of 75 patients diagnosed with MBOT, 27 underwent primary debulking surgery and 48 had FSS. Of the patients who underwent FSS, 28 had USO and 20 underwent ovarian cystectomy. Subsequently, 13 of the 20 patients (65%) who initially had ovarian cystectomy proceeded with completion USO. There were no recurrences following primary debulking, primary USO or completion USO after a median follow up of 49, 65.5 and 39 months, respectively. Four of the 20 patients (20%) who underwent ovarian cystectomy were found to have: residual MBOT (n=1) two months post-cystectomy, MBOT recurrence (n=2) at 10 and 66 months post-cystectomy, or mucinous carcinoma (n=1) five months post-cystectomy, all diagnosed at USO. Conclusions Patients of reproductive age who undergo USO for a MBOT do not require long-term follow-up as the overall risk of recurrence is very low. In contrast, patients who are managed by ovarian cystectomy have a higher risk of recurrence and should be offered long-term surveillance monitoring. Keywords Fertility sparing surgery; Mucinous borderline ovarian tumours; Recurrence of BOT.