A theoretical study of the complexes formed by monosubstituted phosphines (XH2P) and the methyl radical has been carried out by means of MP2 and CCSD(T) computational methods. Two minima configurations have been obtained for each XH2P:CH3 complex. The fist one show small P-C distances and, in general, large interaction energies. It is the most stable one, save in the case of the H3P:CH3 complex. The second minima where the P-C distance are large and resemble a typical weak pnicogen bond interaction show interaction energies between -9.8 and -3.7 kJ mol-1. A charge transfer from the unpaired electron of the methyl radical to the P-X sigma* orbital is the responsible for the interaction in the second minima complexes. The TS structures that connect the two minima for each XH2P:CH3 complex has been localized and characterized.