Introduction Bilateral prophylactic mastectomy (BPM) in women with a high risk of developing breast cancer has shown to provide the greatest risk reduction. Many surgical guidelines recommend the removal of the pectoral fascia (PF) in mastectomies; however, there is no evidence to support this statement. Reported wound-related complications following mastectomy include seroma, flap necrosis, infection and haematoma. Seroma causes discomfort and may delay the reconstructive procedures. Whether removal or preservation of the PF influences drain volume, seroma formation and other postoperative complications following BPM remains unclear. The aim of this study is to assess the impact of removal versus preservation of the PF on drain policy and seroma after BPM. Methods and analysis This is a double blinded, prospective, randomised controlled pilot study with a within-subject design. The inclusion criteria are women >18 years, presenting in the Academic Breast Cancer Centre Rotterdam, who are opting for BPM. Patients with a history or diagnosis of breast cancer are excluded. According to the sample size calculation based on the difference in total drain volume, a number of 21 eligible patients will be included. Randomisation will occur within the patient, which means PF preservation in one breast and PF removal in the contralateral breast. The primary study endpoint is total drainage volume. Secondary study outcomes include time to drain removal, number of needle aspirations, postoperative complications and length of hospital stay. Ethics and dissemination The study is approved by the Erasmus Medical Center Review Board (REC 2020–0431). Results will be presented during international conferences and published in a peer-reviewed academic journal. Trial registration number NCT05391763 ; clinicaltrials.gov