Sr substituted LaInO3 compounds have been prepared by the conventional solid state reaction method. The as-prepared samples are characterized by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential thermal analysis (DTA), thermal expansion coefficient (TEC), and impedance spectroscopy. The XRD analysis of LSI 20 shows the formation of single phase La0.9Sr0.1InO2.95 compound. However, the higher substitution of Sr2+ for La3+ leads to the formation of secondary insulating phase, i.e., SrIn2O4. Sr substitution leads to anionic vacancy which is the possible mechanism for ionic conduction in the given system. Reitveld refinement confirms orthorhombic phase formation in all the samples except LSI 23 (La0.77Sr0.23InO2.89) which is well fitted monoclinic phase. TEC is nearly 9.1 x 10(-6) degrees C-1 in the range of 500-1000 degrees C in LSI 20 sample. The ionic conductivity is 0.11 mS cm(-1) at 800 degrees C in single phase LSI 20 sample. The solid solubility limit is x = 0.20 which is higher than earlier reported values for similar systems.