<p>Mining dam failures have led to long-term contamination of coastal ecosystems, yet the impacts on the early development of marine megafauna such as sea turtles remain poorly understood. The collapse of the Fundão dam in 2015 discharged large volumes of mine tailings into the Rio Doce watershed, reaching important nesting beaches of the loggerhead sea turtle (<i>Caretta caretta</i>). While metal contamination in marine organisms is well documented, there remains a significant knowledge gap regarding the levels of contamination in sea turtles, particularly during embryonic development and across their life stages. This study assessed metal bioaccumulation (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Sb, Sn, and Zn) in the eggs and hatchlings of <i>Caretta caretta</i>, alongside genotoxic effects (micronucleus test) and biochemical responses (catalase and glutathione S-transferase activity) over three nesting seasons (2015/2016, 2016/2017, and 2017/2018). Our results reveal metal bioaccumulation and genotoxic damage in hatchlings, indicating long-term impacts of environmental contamination. We also found maternal transfer of metals to eggs, suggesting that adult females previously exposed to contaminated foraging areas contributed to embryonic exposure. Additionally, the detection of metals in hatchlings linked to contaminated nest sediments points to direct environmental absorption via the eggshell. These findings provide important insights into the ecotoxicological vulnerability of early life stages of sea turtles and underscore the need for long-term monitoring and conservation strategies to mitigate the effects of anthropogenic pollution on endangered marine species. The observed bioaccumulation and genotoxicity may compromise hatchling survival, growth, and fitness, potentially leading to population-level effects and increasing conservation risks for <i>Caretta caretta.</i></p>