<p>Thermodynamics of the interactions of a series of bile salts, sodium deoxycholate (NaDC), sodium cholate (NaC), sodium taurodeoxycholate (NaTDC), and sodium taurocholate (NaTC) with bovine serum albumin (BSA) at pH 7.4 was investigated by isothermal titration calorimetry (ITC). Micellization parameters of bile salts were first determined and then the interaction behavior of bile salts monomers and micelles with BSA was studied. Structurally different bile salts show distinct micellization behavior. A decrease in the number of ring hydroxyls favors micellization. The values of binding constant, Gibbs free energy, enthalpy and entropy provided by ITC demonstrate ionic and hydrophobic contributions to the binding of bile salts with BSA. Binding affinity of bile salts monomers with the protein decreases with decrease in hydrophobicity of bile salts. Fluorescence spectroscopic results corroborate well with the ITC findings. The results exclusively highlight the fact that hydrophobicity of bile salts is the main factor that governs the extent of interaction with the protein. The micellar bile salts do not exhibit binding with the protein. The structural studies of bile salts monomers and micelles with bovine serum albumin as investigated by circular dichroism spectroscopy revealed a significant alteration in the protein conformation. Thermal denaturation study performed using UV–visible spectroscopy shows that the thermal stability of BSA is increased in the presence of both bile salts monomers and micelles. Overall, experimental findings indicated binding behavior of monomeric and micellar bile salt with BSA and their protective effect on BSA by stabilizing the protein in its native state under both the conditions.</p>