The influence of single wall carbon nanotubes SWCNTs and multi wall carbon nanotubes MWCNTs on Vickers microhardness of Gd-123 superconducting phase is studied. Samples of type (SWCNTs)(x) and (MWCNTs)(x)GdBa2Cu3O7-delta, composite where, 0.0 <= x <= 0.1 wt.%, are prepared by solid-state reaction technique. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). Moreover the samples are examined by measuring electrical resistivity and Vickers microhardness. The obtained results showed an enhancement in the phase formation and grains connectivity up to 0.06 and 0.08 wt.% for SWCNTs and MWCNTs added samples, respectively. Likewise the superconducting transition temperature T-c was improved at a low content of CNTs but it suppressed for higher concentrations. In addition, the analysis of Vickers microhardness measurements suggests that the most suitable model that describes the behavior of our sample is proportional specimen resistance PSR model. (C) 2017 Elsevier B.V. All rights reserved.