Abstract: Polycrystalline samples of Ru1-xNbxSr2Gd1.5Ce0.5Cu2O10-delta, 0 <= x <= 0.5, have been synthesized and studied by resistivity, magnetization and ac susceptibility measurements. It was identified a strong suppression of the spin glass (SG) transition, which was totally suppressed in samples for x >= 0.2. The hysteresis loops at low temperatures are the result of the contribution of two distinct magnetic phases: a canted AFM phase and the SG phase. More importantly, the significant changes in the magnetic response of the material affect the superconducting properties of the samples. It was found that both T-c and the superconducting fraction are reduced in samples that show the spin glass phase, possibly due to the magnetic pair breaking effect Ver menos