In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La0.85–x
Na0.15MnO3 (x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group
). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition (T
P). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.