Telomere length is associated with chronic diseases and, in younger populations, may represent a biomarker of disease susceptibility. As growing evidence suggests that environmental factors, including metals, may impact telomere length. We investigated the association between 17 metals measured in toenail samples and leukocyte relative telomere length (RTL), among 472 5- to 7-year-old children enrolled in the Bangladesh Environmental Research in Children's Health (BiRCH) cohortIn single-exposure linear regression models, a doubling of arsenic (As) and mercury (Hg) (μg/g) were associated with a -0.21 (95% CI, -0.032 to -0.010; P = .0005) and -0.017 (95% CI, -0.029 to -0.004; P = .006) difference in RTL, respectively. In Bayesian Kernel Machine Regression (BKMR) mixture models, the overall metal mixture was inversely associated with RTL (P-for-trend < 0.001). Negative associations with RTL were observed with both log2-As and log2-Hg, while an inverted U-shaped association was observed for log2-zinc (Zn) with RTL. We found little evidence of interaction among metals. Sex-stratification identified stronger associations of the overall mixture and log2-As with RTL among females compared to males. Our study suggests that As and Hg may independently influence RTL in mid-childhood. Further studies are needed to investigate potential long-term impacts of metal-associated telomere shortening in childhood on health outcomes in adult life.