Bi_1.6Pb_0.4Sr₂Ca₂Cu₃Oy superconductor samples doped with nanosized samarium oxide (Sm₂O₃) in different amounts (0, 0.05, 0.08, 0.10, and 0.20) were synthesized by a solid-state reaction method and then characterized. The structure and morphology of the samples were characterized by using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Element composition analysis was deployed by energy dispersive X-ray (EDX) spectroscopy measurement. Superconducting transition temperatures of the samples were estimated from dc resistivity (R-T) measurement. XRD showed that both Bi-2223 and Bi-2212 phases coexist in the samples having orthorhombic crystal structure. The volume fraction of Bi-2223 phase showed the highest percentage (77%) for the sample with x = 0.05 addition. It was observed that the volume fraction of Bi-2223 phase decreases and Bi-2212 phase increases with further increasing Sm content. SEM revealed that grain size decreases when the addition content was increased from 0.08 to 0.20 with less inter-coupling between superconducting grains. EDX showed that there are no extra peaks observed except for Sm peaks, confirming that all elements used in the samples were introduced into the Bi-2223 structure. The superconducting transition temperatures T_c,onset and T_c,offset increased for Sm content x = 0.05, but decreased with further addition amount.