Abstract In this study, interaction of a food colouring such as Allura Red AC with Bovine Serum Albumin (BSA) biomacromolecule in 5 mM phosphate buffer, pH=7 was studied by absorption spectroscopy, competitive binding and thermodynamic study. The binding isotherm, binding capacity and Scat chard plots were plotted at various temperatures. The binding constant obtained from the absorption titration data gives a binding constant of 3.38 M-1 at 25º C. The thermodynamic parameters such as binding Gibbs free energy, enthalpy and entropy changes was calculated. The positive values of DH and DS indicated that the process is entropy-driven and suggest that the main driving forces are hydrophobic interaction. Also, the negative ΔG values for the interaction of Allura Red AC with the Bovine Serum Albumin indicate the spontaneity of the interaction.