BackgroundPeople living with multiple sclerosis (plwMS) seek access to information on evidence-based lifestyle-related risk factors associated with multiple sclerosis (MS). As the internet has made delivery of lifestyle information increasingly accessible and cost-effective, we designed the Multiple Sclerosis Online Course (MSOC) to deliver a multimodal lifestyle modification program for plwMS. Two MS online courses were developed: the intervention course based on lifestyle recommendations of the Overcoming Multiple Sclerosis (OMS) program and the standard-care course representing standard lifestyle recommendations from other MS websites. We examined for feasibility in a pilot randomised controlled trial (RCT), where satisfactory completion and accessibility were achieved across both study arms. From this success, a protocol for a larger RCT was developed to examine the effectiveness of MSOC in improving health-related quality of life (HRQoL) and other health outcomes in plwMS.Methods/designThis single-blinded RCT will recruit n = 1,054 plwMS. Participants in the intervention arm will receive access to a MSOC with seven modules providing evidence-based information on the OMS program. Participants in the control group will receive access to a MSOC of identical format, with seven modules providing general MS-related information and lifestyle recommendations sourced from popular MS websites, e.g. MS societies. Participants will complete questionnaires at baseline and at 6, 12, and 30 months after course completion. The primary endpoint is HRQoL, as measured by MSQOL-54 (both physical and mental health domains) at 12 months following course completion. Secondary outcomes are changes to depression, anxiety, fatigue, disability, and self-efficacy as measured by Hospital Anxiety and Depression Scale, Patient-Determined Disease Steps and University of Washington Self-Efficacy Scale, respectively, assessed at each timepoint. Further assessments will include quantitative post-course evaluation, adoption and maintenance of behaviour change from follow-up survey data, and qualitative analysis of participants’ outcomes and reasons for course completion or non-completion.DiscussionThis RCT aims to determine whether an online intervention course delivering evidence-based lifestyle modification recommendations based on the Overcoming Multiple Sclerosis program to plwMS is more effective at improving HRQoL, and other health outcomes post-intervention, compared with an online standard-care course.Trial registrationThis trial was registered prospectively with the Australian New Zealand Clinical Trials Registry,www.anzctr.org.au, identifier ACTRN12621001605886.Date of registration25 November 2021.