The activation of CH bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific CH activation has been developed to date. We herein report an enantiospecific CH activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles. Various compounds, such as amines, amino acids, or peptides, can undergo enantiospecific CH activation/deuteration in the presence of ruthenium nanocatalysts under mild conditions. Theoretical studies revealed a four‐membered dimetallacycle as the key intermediate and suggested that the collective motion of surface species can facilitate the CH activation step by modulating the local electronic structure.