OBJECTIVE: We present the rationale for and the design of a prospective trial to evaluate the role of preoperative frailty and mobility assessments in older women undergoing surgery for the treatment of pelvic organ prolapse (POP) as a planned prospective supplemental trial to the ASPIRe (Apical Suspension Repair for Vault Prolapse In a Three-Arm Randomized Trial Design) trial. The Frailty ASPIRe Study (FASt) examines the impact of preoperative frailty and mobility on surgical outcomes in older women (≥65 years) participating in the ASPIRe trial. The primary objective of FASt is to determine the impact of preoperative age, multimorbidity, frailty, and decreased mobility on postoperative outcomes in older women (≥65 years old) undergoing surgery for POP. METHODS: The selection of the preoperative assessments, primary outcome measures, and participant inclusion is described. Frailty and mobility measurements will be collected at the preoperative visit and include the 6 Robinson frailty measurements and the Timed Up and Go mobility test. The main outcome measure in the FASt supplemental study will be moderate to severe postoperative adverse events according to the Clavien-Dindo Severity Classification. CONCLUSIONS: This trial will assess impact of preoperative age, multimorbidity, frailty, and decreased mobility on postoperative outcomes in older women (≥65 years old) undergoing surgical procedures for the correction of apical POP. Information from this trial may help both primary care providers and surgeons better advise/inform women on their individual risks of surgical complications and provide more comprehensive postoperative care to women at highest risk of complications.