The complete valence shell electron separation energy spectra and momentum distributions are measured for methylamine by high-resolution electron momentum spectroscopy at a total energy of 1500 eV. Many-body calculations of the separation energies and spectroscopic factors using Green's function methods are carried out and compared with the experimental data. The measured momentum distributions are compared with those calculated in the plane wave impulse approximation (PWIA) formalism using an SCF orbital wavefunction which we constructed from a basis set of states that consisted of (10s, 6p, 1d)/[5s, 3p, 1d] for the carbon and nitrogen atoms and (5s, 1p)/[3s, 1p] for each hydrogen atom. The agreement between the measured momentum distributions and the present PWIA-SCF orbital momentum distribution is, in general, fair, although for the outermost valence 7a′ state the SCF wavefunction underestimates the density at low momentum. The inner valence 4a′ and 3a′ orbitals are found to be severely split by the final state correlation effects. The agreement between the measured and calculated spectroscopic factors and separation energies is quite good, although the measured separation energy spectra contain significant strength up to 41 eV, this strength being mainly of 4a′ and 3a′ origin.