While the selective C−F bond activation of perfluorinated toluene (CF 3 C 6 F 5 ) by a trimethylphosphine-supported cobalt(0) complex Co(PMe 3 ) 4 has been achieved in our previous work (Organometallics, 2009, 28, 5771–5776), the proposed mechanism has not been demonstrated directly through quantum chemistry calculations. The present work provides a supplementary theoretical study on a detailed mechanism to better understand the synergistic effect of cobalt center and free PMe 3 ligand on the selective C−F bond activation of CF 3 C 6 F 5 . The calculated results indicate two C−F bonds in CF 3 C 6 F 5 are activated successively via a similar mechanism: the initial oxidative addition of C−F bond to cobalt(0) center, followed by F atom abstraction by a free PMe 3 ligand. However, it is found that the F atom abstraction with a barrier of 34.92kcalmol −1 is the bottle-neck step of the first C−F bond activation, while the oxidative addition of C−F bond is the rate-determining step of the second C−F bond activation with a barrier of 30.85kcalmol −1 . The theoretical results confirm the C−F activation mechanism proposed in our early work, i.e., the Co complex and free PMe 3 ligands cooperatively promote the C−F bond activation.