In this work, novel (1$-x$)(0.75Na${}_{0.5}$Bi${}_{0.5}$TiO₃)-0.25Sr(Zr${}_{0.2}$Sn${}_{0.2}$Hf${}_{0.2}$Ti${}_{0.2}$Nb${}_{0.2}$)O₃-$x$NaNbO₃ (NBT-SZSHTN-$x$NN,$x$ = 0.1, 0.15, 0.2, 0.25) ceramics were fabricated. The influence of co-doping of NN and high entropy perovskite oxide (SZSHTN) on the phase structure, microstructure and dielectric properties of NBT-based lead-free ceramics was investigated. Dense microstructure with a grain size of$\sim$5$\mu$m is observed. When$x$ = 0.25, a wide dielectric temperature stable range of − 35.4–224.3${}^{\circ }$C with a low temperature coefficient of capacitance of$<$ 10% is achieved, fulfilling the industry standard of Y9P specification. Furthermore, excellent energy storage performance with recoverable energy density of 2.4 J/cm³, discharge efficiency of 71%, power density of 25.495 MW/cm³ and discharge rate$<$ 200 ns are simultaneously obtained, which shows great potential for high temperature capacitor applications.In this work, novel (1$-x$)(0.75Na${}_{0.5}$Bi${}_{0.5}$TiO₃)-0.25Sr(Zr${}_{0.2}$Sn${}_{0.2}$Hf${}_{0.2}$Ti${}_{0.2}$Nb${}_{0.2}$)O₃-$x$NaNbO₃ (NBT-SZSHTN-$x$NN,$x$ = 0.1, 0.15, 0.2, 0.25) ceramics were fabricated. The influence of co-doping of NN and high entropy perovskite oxide (SZSHTN) on the phase structure, microstructure and dielectric properties of NBT-based lead-free ceramics was investigated. Dense microstructure with a grain size of$\sim$5$\mu$m is observed. When$x$ = 0.25, a wide dielectric temperature stable range of − 35.4–224.3${}^{\circ }$C with a low temperature coefficient of capacitance of$<$ 10% is achieved, fulfilling the industry standard of Y9P specification. Furthermore, excellent energy storage performance with recoverable energy density of 2.4 J/cm³, discharge efficiency of 71%, power density of 25.495 MW/cm³ and discharge rate$<$ 200 ns are simultaneously obtained, which shows great potential for high temperature capacitor applications.