Here, Tagetes erecta leaves extract mediated silver nanopartices (te-SNPs) were synthesized. This synthesis process was simple, one step and eco-friendly. The te-SNPs were characterized by various spectroscopic instruments such as ultraviolet visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) and Transmission Electron Microscopy (TEM) with energy Dispersive X-ray Spectroscopy (EDS). These te-SNPs showed the effective bactericidal activity against Escherichia coli and Staphylococcus aureus. The interaction of te-SNPs with human serum albumin (HSA) was evaluated by UV-vis absorption, fluorescence (FL), time resolved fluorescence (TRF), DLS and circular dichroism (CD) study. TRF and temperature dependant study suggested that the interaction process followed the dynamic quenching mechanism. The stern-volmer quenching constants (KSV) were obtained as 1.36 x 10(7), 1.51 x 10(7) and 1.94 x 10(7)M(-1)at 288, 298 and 308 K respectively. The thermodynamic parameters were also evaluated and this result suggested that the interaction was spontaneous, and the hydrophobic forces played the most important role for the interaction process. In addition, CD spectra proved minute alteration of secondary structure of HSA upon interaction with the te-SNPs.