A pioneer series of copper(II) complexes bearing planar phenanthroline-modified aromatic ligands and steroid (ethynylestradiol and ethisterone) with generic formula [Cu(N \ N)(steroid)](NO3)2 where N \ N is DPQ, DPPZ and DPPN and steroid is estradiol or testosterone, were synthetized, characterised and screened in vitro and in vivo as antimicrobial agents against Staphylococcus aureus and methicillin resistant Staphylococcus aureus (MRSA). Toxicity studies revealed notable antibacterial activity of the copper – based compounds, which is significantly increased in vivo by the presence of the steroid moiety. Toxicity profiling was estimated in vitro versus Gram-positive (Staphylococcus aureus) and MRSA and in vivo in Galleria mellonella larvae infected with S. aureus. Results showed the complexes to be active against S. aureus and MRSA in vitro (MIC50 average value of 2.46 and 97 lM in S. aureus and MRSA, respectively) and to be active when larvae infected with S. aureus were administered the agents.