Background and Aims: Frailty is highly prevalent in adults with chronic kidney disease (CKD) and is associated with adverse health outcomes. However, exercise training may improve physical function leading to associated improvements in outcomes. The EX-FRAIL CKD trial (ISRCTN87708989) aimed to inform the design of a randomised controlled trial (RCT) that investigates the efficacy of a progressive home-based exercise programme in pre-frail and frail older adults with CKD. Methods: Patients aged ≥65 years with CKD G3b-5 and a Clinical Frailty Scale score ≥4 were eligible for participation. Participants categorised as pre-frail or frail, following Frailty Phenotype (FP) assessment, were randomised to receive a tailored 12-week home-based exercise programme or usual care (UC). Primary outcome measures included recruitment, intervention adherence, outcome measure completion and participant attrition rate. Secondary outcome measures included frailty status (FP), physical function (walking speed, handgrip strength and Short Physical Performance Battery [SPPB]), fall concern (Falls Efficacy Scale-International tool [FESI]), symptom-burden (Palliative Care Outcome Scale-Symptoms RENAL [POS-S RENAL]) and health-related quality of life (Short Form-12v2 [SF-12]). Outcome measures are reported descriptively with 95% confidence intervals (CI) as recommended for pilot trials. Progression criteria to RCT stage were defined as: (1) eligibility: STOP 10%; (2) recruitment: STOP 30%; (3) exercise adherence: STOP: 70%; (4) outcome measure completion: STOP 80%; and (5) loss to follow-up: STOP >50%, GO