The high-temperature oxidation chemistry of methylamine (CH3NH2) has been investigated by elucidating the major reaction paths under flow reactor conditions. A comprehensive detailed chemical-kinetic mechanism is proposed, which is comprised of 350 elementary reactions and 65 reactive species. A set of pyrolysis and oxidation reactions of CH3NH2, combined with the literature H-C-O-N reaction chemistry, constitute the proposed mechanism. In addition, the reactions of H-abstraction from both the C- and N-atom centers of CH3NH2, have been incorporated into the mechanism. Good agreement between model predictions and experimental data is obtained over fuel-to-oxygen equivalence ratios ranging from 0.1 to 1.7, for 600-1400 K temperature range, and for subatmospheric (0.01 atm) as well as for atmospheric flow conditions. A reaction path analysis was conducted using the integral averaged reaction rates, and the major reaction pathways were identified. A first-order sensitivity analysis for species CH3NH2, NO, and HCN was performed and the results are compared with the reaction-path analysis.