A magnetic recording medium, a composition for it, and a magnetic recording and reproducing apparatus are provided. The medium includes a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the support. The magnetic layer also includes a compound including one or more partial structures selected from partial structures represented by Formulas 1 and 2, and a polyalkyleneimine chain. The composition for the recording medium includes a ferromagnetic powder and the compound. In Formulas 1 and 2, L1 and L2 each independently represents a divalent linking group, Z1 and Z2 each independently represents a monovalent group represented by —OM or a monovalent group represented by —O−A+, M represents a hydrogen atom or an alkali metal atom, and A+ represents an ammonium cation.