We study iron oxide nanoparticles stabilized by citrate ligands interacting with long linear poly(acrylamide) chains in the regime where the diluted chains are decorated by many smaller magnetic nanoparticles. The strength of adsorption of the particles onto polymer increases when the unbound citrate concentration decreases, as evidenced by the faster translational dynamics of the particle‐polymer complexes and the slower rotational dynamics of the nanoparticles. © 2004 American Institute of Physics