Owing to industrial and technological developments, there has been an increasing demand for piezoelectric ceramics that can function at temperatures of 500°C or higher. Na0.5Bi4.5Ti4O15 (NBT) with its high Curie temperature (TC) of 650°C is a typical bismuth layer–structured ferroelectric. However, its relatively low piezoelectric coefficient (d33 ∼ 16 pC/N) hinders its potential application at high temperatures. In this study, compositions of Ca0.05(Na0.5Bi0.5)0.95Bi4Ti4O15 with different additions of Cr2O3 (CNBT–Cr100x) were designed based on previous studies on Ca2+‐doped NBT piezoceramics, and the effects of the addition on the structural and electrical properties were investigated. The d33 value of CNBT–Cr20 was as high as 29 pC/N, almost twice higher than that of pure NBT ceramics. This increase was investigated in depth using X‐ray diffraction refinement and piezoelectric force microscopy in terms of intrinsic and extrinsic contributions. The Ps values of CNBT and CNBT–Cr20 were almost equal. The density of the domain walls of CNBT–Cr20 was significantly higher than that of CNBT, indicating that the increase of d33 of CNBT–Cr20 is mainly due to the increase in the extrinsic contribution. The CNBT–Cr20 ceramic exhibited excellent properties with a high TC of 655°C, a high d33 of 29 pC/N, and a resistivity high than 106 Ω cm at 500°C, demonstrating its potential for applications at high temperatures such as 500°C.