Background: Given the inverse relationship described previously between telomere content and thyroid subsequent malignant neoplasm (thyroid SMN) in survivors of childhood cancer, we investigated the relationship between known genetic determinants of leukocyte telomere length (LTL) and thyroid SMN among survivors. Methods: Leveraging data from a large, genotyped survivor cohort, the Childhood Cancer Survivor Study, we used a well-described genetic risk score method to estimate the HR for thyroid SMN among 5,324 genotyped survivors. Results: We identified 118 survivors with thyroid SMN and 5,206 without thyroid SMN. No association between genetically estimated LTL and risk for thyroid SMN was identified. Conclusions: Our results suggest that variation in common SNPs influencing LTL is not strongly associated with risk for thyroid SMN in survivors of childhood cancer. Impact: The previously observed inverse relationship between LTL and thyroid SMN risk in survivors of childhood cancer may be related to alternative molecular mechanisms and warrants further study.