Performance status is an important concept in oncology, but is typically clinician-reported. Efforts are underway to include patient-reported measures in cancer care, which may improve patient symptoms, quality of life and overall survival. The purpose of this study was to gain a preliminary understanding of how patients determined their physical performance status based on a novel patient-reported version of the Eastern Cooperative Oncology Group Performance Status (ECOG) scale. We conducted qualitative interviews, including concept elicitation and cognitive interviewing as part of the Patient Reports of Physical Functioning Study (PROPS) to investigate how participants selected their answers to a novel patient-reported ECOG. Participants were administered the patient-reported ECOG and asked to describe devices and modifications used to keep up with daily activities. Participants generally understood the ECOG as intended. Participants with recent changes in status had some difficulty selecting an answer. Most participants used modifications and assistive devices in their daily lives but did not incorporate these into their rational for the ECOG. The potential benefits of a patient-reported ECOG are numerous and this study demonstrates that participants were able to understand and answer the patient-reported ECOG as intended. We recommend future evaluation for the most-appropriate recall period, whether to include modifications in the ECOG instructions, and if increasing the number of response options to the patient-reported ECOG may improve confidence when providing an answer.