Introduction:Preliminary research has shown the effectiveness of supervised exercise-based interventions in alleviating sequela resulting from metastatic prostate cancer. Despite this, many individuals do not engage in sufficient exercise to gain the benefits. There are many barriers which limit the uptake of face-to-face exercise in this population including lack of suitable facilities, remoteness, access to experts, significant fatigue, urinary incontinence, and motivation. Technology-enabled interventions offer a distance-based alternative. This protocol describes a pilot two-armed randomised controlled study that will investigate the feasibility and preliminary efficacy of an online exercise and behavioural change tool (ExerciseGuide) among individuals with metastatic prostate cancer.Methods:Sixty-six participants with histologically diagnosed metastatic prostate cancer will be randomised into either the eight-week intervention or a wait-list control. The intervention arm will have access to a tailored website, remote supervision, and three tele-coaching sessions to enhance support and adherence. Algorithms will individually prescribe resistance and aerobic exercise based upon factors such as metastasis location, pain, fatigue, confidence, and current exercise levels. Behavioural change strategies and education on exercise benefits, safety and lifestyle are also tailored through the website. The primary outcome will be intervention feasibility (safety, usability, acceptability, adherence). Secondary exploratory outcomes include changes in physical activity, quality of life, sleep, and physical function. Outcomes will be measured at baseline and week 9.Discussion:The study aims to determine the potential feasibility of an online remotely-monitored exercise intervention developed for individuals with metastatic prostate cancer. If feasible, this pilot intervention will inform the design and implementation of further distance-based interventions.Trial registration: ANZCTR, ACTRN12614001268639. Registered 10th December 2018, https://anzctr.org.au/ACTRN12618001979246.aspxProtocol issue: Version 1 (9th March 2020).