High-performance lead-free piezoelectric materials have become a hot topic in the field of advanced functional materials. In 2009, the (1 − x)Ba(Zr_0.2Ti_0.8)O₃–x(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) system with surprisingly high piezoelectric properties was first proposed by Liu and Ren; as a milestone discovery in the field of ferroelectrics, it has aroused extensive attention. In this review, initially, we highlight the remarkable electrical properties of the BZT–BCT system, and then summarize the advances in the BZT–BCT material based on five aspects including the origin of its high properties, preparation and poling, grain size control, chemical modification and texture design. We focus on a systematic discussion of its phase boundaries, domain structure, and defect chemistry in relation to improved dielectric and piezoelectric properties. In addition, the device performance of BZT–BCT materials is also evaluated. Due to their excellent comprehensive properties, BZT–BCT materials have been widely studied in various applications such as energy harvesters, flexible sensors and energy storage capacitors. Finally, based on the state-of-the-art knowledge, we present an outlook on the challenges and application prospects of BZT–BCT materials. This review will help promote the practical applications of BZT–BCT materials, and accelerate the development of lead-free ferroelectric materials in specific fields.