We report herein a comprehensive study of gas-phase reactions of Co+ with ethylamine using density functional theory. Geometries and energies for all the stationary points involved in the reactions are investigated at the B3LYP/6-311 ++.G(2df,2pd) level. Six different "classical" N and "nonclassical" ethyl-H attached isomers are found for the Co+-ethylamine complexes. The classical complexes are much more stable than the nonclassical ones, which have the complexation energies close to Co+ complexes with small alkanes. Extensive conversions could occur readily between these encounter complexes. All conceivable reaction pathways from each encounter complex to the experimentally observed,products are carefully surveyed, and the most likely reaction mechanisms are derived. Activation of the C-alpha-H bond of ethylamine by Co+ through both the classical and nonclassical complexes leads to not only the. H-2 loss but also the hydride abstraction. The loss of ethylene arises from Co+ insertion into the polar C-N bond in the classical complexes as well as from C-beta-H activation through the nonclassical methyl-H attached complex of Co+-gauche-ethylamine. CH4 only forms via C-C activation from the nonclassical complex with the metal bound to two Hs from the different carbons. Initial N-H insertion is unlikely to be important. It is the reactions of the nonclassical complexes that closely parallel with the Co+ + alkane reactions. The theoretical work sheds new light on the title reactions and can serve as a theoretical approach to the reaction mechanisms of transition metal ions with primary amines.