Background <p>Patient-reported outcomes (PROs) are essential for measuring the effectiveness of medical treatments from the patient’s perspective. PROs are typically defined as any measure that describes or reflects how a patient feels, functions, or survives, and are becoming increasingly important in regulatory decision making. The administration of PROs in clinical studies is often described as burdensome for both patients and trialists. This research aimed to examine the acceptable PRO burden from the perspective of patients and trialists, in the context of oncology clinical trials.</p> Methods <p>This was a mixed-methods study, comprised of semi-structured qualitative interviews with oncology trialists and an online survey with people with cancer who reside in the United States, Canada, and Europe.</p> Results <p>Nine trialists and 90 patients (M = 49.6 years old) with cancer took part in the study. Three overarching themes were identified across the collected data. The first theme describes the benefits of including PROs in oncology studies. The second theme describes the acceptable burden associated with PROs features, such as length, clarity, and relevance of items. The third theme describes implementation-related burden, such as frequency of assessment and use of ePROs.</p> Conclusions <p>Both patients and trialists are willing to accept some of the burden associated with PRO administration in oncology clinical trials. Further research is needed to better understand how to best mitigate the challenges that increase respondent burden, over the threshold of acceptable burden within oncology clinical trials and beyond.</p>