Abstract: This study concern to the kinetic and mechanism studies of interaction between L- tyrosine (L-T) and iodine upon UV-Vis spectrophotometric measurements. The results showed that the reaction is first order respect to each reactant by using the initial rate method. Also, the rate constant of the reaction at two different temperature 25.0 and 15.0°C were determined. Then the resulting activation functions such as Ea,ΔH#,ΔG#,ΔS# and frequency factor, A, were calculated. The resulted values at 25.0°C are: Ea = 36.82 kJ mol-1, A = 2.032x106 L mol-1 sec-1,ΔG°# = 73.17 kJ mol-1,ΔH°# = 34.34 kJ mol-1 andΔS°# = -132.4 J mol-1 K-1.