In this study, the surface of magnetic nano-Fe3O4 was successfully loaded and modified by dioctyl phthalate (DOP) and the produced sorbent was further combined with triethylenetetamine in a solvent free procedure for the formation of a novel magnetic nano-Fe3O4-DOP-TETA sorbent. The produced nano-particles were found in the order of 3.0–12.0 nm and characterized by different shapes and morphologies, high magnetic properties and good thermal stability. The surfaces of these magnetic nano-sorbents were also identified by the presence of a variety of surface functional groups, certain incorporated selectivity properties and good magnetic solid phase sorption behaviors. The experimental controlling parameters affecting the metal sorption properties were also studied and optimized and the results of Cd(II), Pb(II) and Ni(II) up-take confirmed the high dependence on reaction pH, contact time, sorbent dosage, effect of initial metal ion concentration and presence of competing ions such as Cu(II). Generally, the evaluated sorbents were characterized by strong tendency and high selectivity characters toward binding with Cd(II) and Pb(II) under all evaluated and optimized controlling conditions. The potential applications of magnetic nano-sorbents as magnetic solid phase extractors for Cd(II) and Pb(II) from drinking tap water, industrial wastewater and sea water were evaluated using multi-stage micro-column technique and excellent results were obtained in the range of 82.3–100.0 ± 3.0–5.0%, respectively.