In the title compound, [Fe(C(5)H(5))(C(6)H(16)P(2))(CO)](C(12)H(13)BOP), the Fe(II) ion adopts a three-legged piano-stool geometry, with Fe⋯Cg = 1.721 (5)Å (Cg = the centroid defined by the C atoms of the cyclo-penta-dienyl ring). The 1,2-bis-(dimethyl-phosphino)ethane (dmpe) ligand chelates to form a five-membered C(2)P(2)Fe ring which is in a pseudo-half-chair conformation. In the crystal structure, associations of one cation and two anions are formed via weak inter-molecular C-H⋯O hydrogen bonds, giving rise to R(4) (2)(9) rings.