Nanoparticle-protein conjugates are promising probes for biological diagnostics and versatile building blocks for nanotechnology. Here we demonstrate the interaction of SeNPs with BSA macromolecule simply by physical adsorption method. The interaction between SeNPs and BSA has been investigated by UV-Vis, fluorescence, circular dichroism (CD) spectroscopic and thermal methods. The esterase-like activity of BSA towards PNPA was investigated in the presence of SeNPs. The effects of SeNPs on the stability and conformational changes of BSA were studied, which indicated that the binding of SeNPs with BSA induced relative changes in secondary structure of protein. SeNPs acted as a structure stabilizer for BSA which was further confirmed by thermal denaturation study. The hydrophilic bonding forces played important roles in the BSA-SeNPs complex formation. The putative binding site of SeNPs on BSA was near to Sudlow's site II. The hydrophilic interaction of SeNPs on the stability and structure of BSA would find promising application in drug delivery system.