We have investigated the sintering behavior of Sr hexaferrite ( SrFe 12 O 19) and the effects of adding CuO , which partly substituted for the Fe 2 O 3 and the Fe deficiency during the sintering. For the experiments, samples with nominal compositions of SrCu x Fe y−x O 19−δ (x = 0–1.0, y = 11–12) were prepared with a solid-state reaction at 1000°C. The overall shrinkages and the shrinkage rates were followed using dilatometry during the sintering. The addition of CuO was found to enhance the sintering rate of the Sr hexaferrite significantly at temperatures below 1100°C, whereas the Fe deficiency had only a moderate effect on the sintering above 1100°C. The relative densities of the Sr hexaferrite ceramics containing Cu sintered at 1000°C for 3 h were above 90%, whereas the Cu -free Sr hexaferrite ceramics only started to sinter at 1000°C. We have shown that the addition of CuO enabled the reactive liquid-phase sintering of Sr hexaferrite at 1000°C.