In this work, we present the impact of using Na2CO3 as a sintering aid and grain growth agent on the crystal structure, microstructure, and piezoelectric properties of (Bi0.5Na0.5)TiO3 ceramics. The addition of Na2CO3 leads to a substantial increase in the grain size and density even at a reduced sintering temperature of 1025 °C. However, at the same time, the value of the piezoelectric constant d33 drops dramatically. Using high-resolution x-ray diffraction analysis, we demonstrate that the decrease in piezoelectric constant is due to a change in the chemical composition of the (Bi0.5Na0.5)TiO3 base material rather than due to the change in the grain size. High Na2CO3-addition levels lead to the formation of Bi2O3 as a secondary phase during sintering too.