A novel type of magnetic composite particles was constructed using helical poly(n-hexyl isocyanate) and Fe₃O₄. For this purpose, well-defined 4-ethynylbenzyloxy-terminal poly(n-hexyl isocyanate)s (PHIC–CCs) were synthesized via coordination polymerization by using an organotitanium catalyst. The PHIC–CCs were characterized by GPC, FT-IR and ¹H NMR techniques. UV-vis absorption spectra demonstrated that the PHIC–CCs adopted dynamic helical structures in tetrahydrofuran. Azide-modified magnetic Fe₃O₄ nanoparticles (Fe₃O₄@N₃ NPs) were prepared through the reaction between 3-azidopropyltrimethoxysilane and oleic acid-coated magnetic Fe₃O₄ NPs. The obtained clickable PHIC–CC and Fe₃O₄@N₃ NPs were subjected to the Cu-catalyzed azide/alkyne cycloaddition for synthesizing the anticipated Fe₃O₄@PHIC composite NPs. FT-IR, TGA and TEM techniques confirmed the formation of the magnetic composite nanoparticles. UV-vis absorption spectra demonstrated that the PHIC chains coated on the magnetic Fe₃O₄ NPs adopted dynamic helical structures. XRD measurements revealed that coating PHIC chains on Fe₃O₄ nanoparticles did not change the phase properties of Fe₃O₄ nanoparticles. The Fe₃O₄@PHIC composite NPs showed a saturation magnetization of 17.8 emu g⁻¹ and the expected rapid magnetic responsivity.