The COVID-19 pandemic has posed tremendous challenges to healthcare systems. Care for oncology patients, a vulnerable population during the pandemic, was disrupted and drastically changed. A multicenter qualitative study was conducted in 11 Belgian hospitals with the aim to provide an overview of the most important changes that were made in the care of oncology patients in Belgium. In each hospital, a nurse or physician was interviewed by telephone. Two rounds of structured interviews—during the first and second waves of the pandemic—were conducted. The data were analyzed using content analysis. The impact of COVID-19 on care practices for patients with cancer was enormous during the first wave. Major changes, including good but also less patient-centered practices, were implemented with unprecedented speed. After the initial wave, regular care was resumed and only limited new care practices were maintained. In only a few hospitals, healthcare teams reflected on lessons learned and on the maintenance of good practices that came from the COVID-19 experience. As a result, opportunities for healthcare innovation and quality improvement seemed to be missed. Our recommendations aim to support policymakers, hospital managers, and healthcare professionals to learn from the COVID-19 pandemic and to drive patient-centered initiatives in future cancer care.