Introduction: The potential of patient symptoms being monitored longitudinally in radiotherapy (RT) is still unexploited. When novel technologies like online adaptive MR-guided radiotherapy (MRgRT) are evaluated, weekly electronic patient-reported outcomes (ePROs) may add knowledge about the symptom trajectory. This study aimed at evaluating feasibility, usability and acceptance of weekly ePRO among patients receiving pelvic radiotherapy. Materials and Methods: In a mixed-methods convergent design, a prospective pilot study enrolled patients referred to pelvic radiotherapy with curative intent. Patients used their own device at home to self-report PRO weekly during and four weeks following radiotherapy and week 8, 12, and 24 (paper-questionnaire as an alternative). Feasibility was extracted from the ePRO software. The Patient Feedback Form and patient interviews were used to explore usability and patient acceptance. Patients were informed that clinicians had no access to PRO responses. Results: In total, 40 patients were included; 32 patients with prostate cancer and 8 with cervical cancer (consent rate 87%), median age 68 (36–76). The majority did digital reporting (93%). 85% of patients responded to ≥80% of the weekly questionnaires with 91% average adherence to weekly completion (60% for follow-up), although lower for patients ≥age 70. Time spent on ePRO (97%) and frequency of reporting (92%) was considered appropriate. Interviews (n = 14) revealed the application was usable and the patients requested real-time feedback from the clinicians. Conclusion: Recruitment for ePRO during radiotherapy was feasible and adherence to weekly self-reporting high. The digital application was usable and weekly frequency and time spent acceptable. Real-time feedback from the clinicians is requested by the patients.