The energy storage density of a Ba0.4Sr0.6TiO3 ceramic with the addition of 5–20 vol% glass was investigated. The results show that the improvement of the energy density in glass‐added Ba0.4Sr0.6TiO3 samples arises due to two factors: one is that the breakdown strength is notably improved due to the decrease of the porosity and the reduction of the grain size and pore size in glass‐added samples and the other is that the remnant polarization of glass‐added samples is decreased. The energy density of the samples containing 5 vol% glass additive was improved by a factor of 2.4 compared with that of pure Ba0.4Sr0.6TiO3.