Backgrounds: With the rapidly growing number of long-term survivors of childhood cancer, knowledge of the possible influences of the cancer experience on the child’s adjustment, educational functioning, and social relationships has been an increasingly important issue. In this study, we addressed the issues of peer relationships, school attendance, and academic achievement of childhood cancer survivors in Korea. Materials and Methods: Between July 2015 and December 2016, 15 institutions in Korea participated in this study on behalf of the Korean Society of Pediatric Hematology and Oncology. We studied 241 children diagnosed with cancer who, at the time of the study, were older than 9 years. The self-reported paper-and-pencil questionnaire was used in this study. Results: Approximately 21% of the survivors suffered from a lack of friends. Bullying was reported by 30.2% of survivors. Survivors who returned to primary school reported a higher incidence of bullying compared to survivors who returned to middle or high school (p=0.03). The percentage of children who missed classes more than 4 days in a month was higher in survivors with brain tumors than those with other tumors (p=0.04). Children reporting better relationships with friends showed less difficulty in learning (p0.01) and overall higher academic performance (p=0.03). Approximately 41% of children reported learning difficulty, mainly due to the difficulty in understanding the materials (58.0%) or concentrating in classes (28.7%). After returning to school, 52.7% of the patients reported that they had lower overall mark averages than they had before. Patients who returned to high school showed the highest rate of repeating a grade (p=0.05) and the lowest rate of achieving high academic marks (p0.01). The school marks in the Korean language (p=0.03), English (p=0.04), and physical education (p=0.04) were worse for the children with brain tumors than for the children with other tumors. Conclusion: Our findings suggest that school-organized educational support on returning to school was crucial, and that high school students with cancer have more difficulties in academic performance than younger children. Particular concern is needed to for patients with brain tumors with timely intervention to assist their education to overcome poor language and physical function.