Background <p>Accurate adverse event (AE) reporting is critical to the success of clinical trials; over the last 10 years, momentum has been building to collect AE data directly from the patient. In this study, we investigated the use of an electronic, web-based platform by which cancer clinical trial patients self-reported AE data. In this report, we explored the perceptions and experiences of participants using the platform during participation in an interventional clinical trial.</p> Methodology <p>Patients consenting to an interventional clinical trial run by a cancer clinical trial unit at a tertiary hospital in Australia were eligible for enrolment. Participants used an online platform to report symptomatic data weekly over 26 weeks. Participant feedback on the platform was collected via an implementation survey at baseline, week 12, and week 26 and a qualitative interview at week 26.</p> Results <p>Participants agreed that the platform was acceptable, appropriate, and feasible in its purpose. This agreement remained throughout their participation on the study. Qualitative analysis of interview data revealed three major themes: accessibility and useability, platform functionality, and personal attributes and benefits/burdens. Participants reported areas for improvement, primarily around platform functionality and consideration of symptom burden limiting participant capacity to engage with the platform.</p> Conclusions <p>To our knowledge, this is the first study that investigates, in-depth, the participant experience of self-reporting cancer clinical trial AE data via an electronic platform. Our study lends evidence from the participant-perspective to previously-reported studies investigating the feasibility of collecting AE data directly from the patient. Participants agreed that the platform was feasible and would be of benefit to future cancer clinical trial participants.</p>