The paper presents the experimental studies of reinforced concrete column (RC column) capacity affected by core drilling. By testing three groups (9 total) of full scale concrete short columns, the experiment demonstrates that the axial compression capacity of RC columns after core drilling is reduced from 5.63% to 22.14% while the ultimate displacement decreases from 1.88% to 26.14%. The behavior of columns is altered from the axial compression failure to a small-eccentricity compression failure. The paper summarizes experiment results, followed by an investigation of the dominant factors, such as column effective cross section, drilling location, drilled hole repairing and reinforcing steels discontinued by drilling, that have impact on RC column capacity. The rationale of capacity variations of RC columns due to core drilling is also investigated.