Objective: This study aims to establish the characteristics of second primary neoplasms (SPNs) and the long-term follow-up status of a tertiary pediatric oncology center. Methods: Records of 1799 patients followed up in the pediatric oncology division between January 1981 and December 2022 were evaluated retrospectively. Results: Thirty-four (1.9%) cases of secondary neoplasms were identified throughout 41 years. The 5-year and 10-year cumulative incidence was 1% and 4%, respectively. The three most common SPNs were thyroid carcinomas, central nervous system (CNS) tumors, and leukemias. The shortest median latent period of SPN detection was 15.5 (2-35) months in secondary leukemias, while 8 (0-17) years in all SPNs. Secondary solid tumors that occurred within the radiation field were thyroid carcinomas and meningiomas with a 5.5 (3-12) and 16 (6-22) years latency period, respectively. Ten patients died; the median death time from the diagnosis of SPN was ten months in all secondary leukemias and 3,5 months in CNS tumors. The 5-year overall survival was 91%, with a median follow-up time of 13.1 years in all patients with SPN. Conclusions: Considering the SPN-inducing effects of radiotherapy and chemotherapy, patient-protective improvements in treatment protocols are required. Multidisciplinary and long-term follow-up is essential even in adulthood because of the long latency period of some SPN occurring in pediatric cancer survivors