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Interplay between hydrogen and nanovoids, despite long-recognized as a central aspect in hydrogen-induced damages in structural materials, remains poorly understood. Focusing on tungsten as a model BCC system, the present study, for the first time, explicitly demonstrated sequential adsorption of hydrogen adatoms on Wigner-Seitz squares of nanovoids with distinct energy levels. Interaction between hydrogen adatoms on the nanovoid surface is shown to be dominated by pairwise power law repulsion. A predictive model was established for quantitative prediction of configurations and energetics of hydrogen adatoms in nanovoids. This model, further combined with equation of states of hydrogen gas, enables prediction of hydrogen molecule formation in nanovoids. Multiscale simulations based on the predictive model were performed, showing excellent agreement with experiments. This work clarifies fundamental physics and provides full-scale predictive model for hydrogen trapping and bubbling in nanovoids, offering long-sought mechanistic insights crucial for understanding hydrogen-induced damages in structural materials.Being the most abundant element in the known universe and a typical product from corrosion, hydrogen (H) exists virtually in all service environments. The exposure of metallic materials to H-rich environments can result in numerous structural damages, including H induced cracking 1, 2 , H induced surface blistering/flaking 3-7 , and H induced porosity/swelling 8-13 , among others. These damages undesirably degrade the structural and mechanical integrity of materials 14-16 , often causing premature and even catastrophic failures 4, 6, 17 , and thus jeopardizing safety and efficiency of many applications. It's generally believed that these damages originate from interactions between H and various lattice defects. One key issue among those interactions is the H interplay with nanovoids, which promotes the formation and growth of mesoscale H bubbles and consequently leads to experimentally observable failures in structural materials 3-11, 15, 16, 18 .