This work studied X-ray powder diffraction (XRD), electrical resistivity and electron paramagnetic resonance (EPR) measurements for Bi 1.8Pb 0.4Sr 2Ca 2.1Cu 3− x Ru x O 10+δ (0.0 ≤ x ≤ 0.4) superconducting samples. XRD analysis and electrical resistivity data showed that the low-content of Ru, x ≤ 0.05, enhanced both the phase formation and the superconducting transition temperature of (Bi, Pb)-2223 phase. A phase change from (Bi, Pb)-2223 phase to (Bi, Pb)-2212 phase was reported for x ≥ 0.15. Two EPR lines were observed for 0.0 ≤ x ≤ 0.075, indicating the presence of both (Bi, Pb)-2223 and (Bi, Pb)-2212 phases. While, one EPR line was observed for x ≥ 0.15, corresponding to the (Bi, Pb)-2212 phase formation. The number of spins ( N) participating in the resonance and its spin paramagnetic susceptibility (χ), for the two phases, were calculated as a function of both Ru-content and temperature. In addition, we reported the variation of activation energy ( E a ), Curie constant ( C), Curie temperature ( θ) and effective magnetic moment ( μ) with Ru-content.