The kinetics of ruthenium(III) catalysed oxidation of L-lysine by hexacyanoferrate(III) in aqueous alkaline medium was studied spectrophotometrically at constant ionic strength of the medium. The reaction shows first order dependence on oxidant, substrate and the catalyst. Initial addition of reaction products did not affect the rate significantly. The active species of catalyst and oxidant have been identified. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III) – L-lysine complex, which further reacts with one molecule of hexacyanoferrate(III) in a rate determining step followed by other fast steps to give the products. The main products were identified. The activation parameters with respect to the slow step of the mechanism are computed and discussed and thermodynamic quantities are also determined. A mechanism involving the formation of a complex between active species of catalyst and lysine has been proposed.