The influence of chelating agents (organic acids with different structures) on iron oxides and hydroxyapatite nanoparticle (NP) morphology obtained by two different synthetic procedures (precipitation method and hydrothermal synthesis) were studied. The relationship between the synthetic conditions and the nature of the growth limiters or NP morphology regulation agents was considered. The mechanism of the NP growth regulation and the general peculiarities of this process for materials with different chemical natures are also discussed. It was concluded that the use of chelating agents dramatically changes the NP size and shape and the degree of modification is determined by the binding force between chelating agent and ions on NP surfaces.