Purpose This study was designed to determine the changes in the quality of life (QOL) and occupational performance of children with cancer and to examine their rehabilitation needs during the pandemic period in Turkey. Methods 60 children with cancer and their families participated in the study. The first and second assessments were carried out in April and September 2020, respectively. The pediatric quality of life inventory parent proxy-report was used to evaluate the QOL, and the Canadian occupational performance measurement was used to evaluate children's occupational performance and satisfaction. A qualitative interview was planned to determine the impact of the pandemic on children with cancer alongside their families and therefore determining the rehabilitation needs of the children. Results While there is no statistically significant change in the pain-related conditions of the children in the first six months of the pandemic (p > 0.05), procedural and treatment anxieties of the children increased during the treatment. Their QOL including cognitive state, perceived physical appearance and communication skills also showed a statistically significant decrease (p < 0.05). Both the occupational performance and satisfaction scores decreased significantly, covering the pre-pandemic and pandemic era (p < 0.01). In the qualitative interview parents expressed their children's need for physical, psychological and social participation support. Also, they emphasized the need for time management. Conclusions During the COVID-19 pandemic, the QOL and occupational performance level of children with cancer decreased significantly. Holistic rehabilitation approaches complying with pandemic conditions are likely to benefit these children.