Abstract: Complexes containing cobalt and carbon monoxide ligands, CO releasing molecules (CORMs), have the potential of anti-tumor and anti-inflammatory. In this paper, three hybrid CORMs 1-3 were synthesized and tested for their toxicology in vivo and bioactivities. The results suggest that the complexes have a long half-life in the range of 43-53 min; their oral LD₅₀ to mouse are between 1 500 mg·kg^-1 and 5 000 mg·kg^-1. After the successive administration, complex 1 exhibited a toxic activity in rats' liver, and induced an injury to liver cells. Complex 1 had a strong growth inhibition activity (IC₅₀ 36.20 μmol·L^-1 and 39.25 μmol·L^-1) in both HeLa cells and HepG2 cells, complex 2 displayed a lower activity in the inhibition of HeLa cells proliferation than the control 5-FU (IC₅₀ 114.19 μmol·L^-1), but had a higher activity in the inhibition of HepG2 cells than the control 5-FU (IC₅₀ 171.34 μmol·L^-1). The anti-inflammatory study suggests that all of them reduce intracellular nitrite level, complexes 1 and 2 have a stronger activity than complex 3. Their anti-inflammatory activity attributes to the CO molecules of the CORMs, which was confirmed by comparison with the corresponding ligand.