The gas-phase reaction mechanisms of methylamine (MA) with the ground-state Co+ (F-3) and Ni+(D-2) are theoretically investigated using density functional theory at both the B3LYP/6-311++G(d p) and B3LYP/6-311++G(3df 2p) levels The reactions for hydride abstraction and dehydrogenation are analyzed in terms of the topology of potential energy surfaces (PESs) Co+ and Ni+ perform similar roles along the isomerization processes to the final products Hydride abstraction takes place via the key species of metal cation-methyl-H intermediate followed by a charge transfer process before the direct dissociation of CH2NH2+ MH (M = Co Ni) The enthalpies of reaction stability of metal cation methyl H species and competition between different channels account for the sequence of the hydride abstraction products CoH < NiH < CuH The most competitive dehydrogenation route occurs through a stepwise reaction consisting of initial C-H activation amino-H shift, and direct dissociation of the precursor CH2NHM+ H-2 This theoretical work sheds new light on the experimental observations and provides fundamental understanding of the reaction mechanism of amine prototype with late first-row transition metal cations