Trapping of ion‐implanted deuterium (D) by irradiation defects and He bubbles in Mo was investigated through nuclear‐reaction profiling of the D during linear ramping of temperature. Resulting data were analyzed using transport theory to obtain trap strengths. Nanometer‐size He bubbles were found to trap the D with a binding enthalpy of 1.15±0.15 eV relative to the solution site, consistent with two independent predictions based, respectively, on effective‐medium theory and thermodynamic analysis. Implantation damage trapped the D with three different binding enthalpies, 1.15, 1.03, and 0.80 eV, attributed, respectively, to vacancy clusters, monovacancies with low D occupancy, and monovacancies with high D occupancy. The two latter values are in good agreement with effective‐medium theory.