In this work, a comparative study of the effect of the NCD size as a stabilizing agent, on the synthesis of copper nanoparticles (Cu-NPs) by an easy green method was reported. The nanoparticles were synthesized through the chemical reduction of aqueous solutions of copper (II) sulfate with ascorbic acid, using different native cyclodextrins (NCDs) (α-, β-, or γ-NCD) as stabilizing agents. Cu-NPs were characterized by scanning electron microscopy–energy dispersive spectroscopy (SEM–EDX), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pattern showed in the typical selected area electron diffraction (SAED) and lattice fringes, evidence that the crystalline structure of Cu-NPs is face-centered cubic (FCC) with a (1 1 1), (2 0 0) and (2 2 0) lattice planes of Cu. The analysis of the TEM images show that the size of the Cu-NPs depends on the type of native cyclodextrin (NCD), also it was observed that the nanoparticles are spherical and with a size between ∼2 and 33 nm. The smaller Cu-NPs were obtained with α-NCD (mode 4 nm), while the nanoparticles obtained with β-NCD show the narrow size distribution (mode 6.5 nm). The average particle size and particle size distribution of Cu-NPs depend upon the type of CDs.