In this paper, a multi-analytical-technique approach was utilized to investigate the property of the complexes of Dy3+, Er3+, Yb3+ with caffeic acid (HCaf) and 1,10-phenantroline (Phen). The synthesized complexes were analyzed using FT-IR and thermal (TGA) analysis. IR spectroscopy results indicated the successful synthesys of these complexes, with three of them consist of neutral monomeric molecules.Thermal analysis demonstrated their considerable heat stability. The general molecular formula for the synthesized complexes in solid state was Ln(Caf)3Phen (Ln: Dy, Er, Yb). These results were confirmed by electrospray-ionization mass spectrometry (ESI-MS). Additionally, the antimicrobial properties of thecomplexes and HCaf against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were studied by measuring the diameter of the inhibitory zone. The complexes present higher antibacterial activity against bacterias compared to HCaf, likely due to the increased lipophilicity of these complexes.