Abstract Low ambient temperatures drastically decelerate the strength development of cementitious materials, which shortens the construction season in cold regions. The use of ground-granulated blast furnace slag (GGBFS) in concreting works is usually avoided in winter because of its slower hydration rate relative to Portland cement (PC). In this study, the impacts of calcium silicate hydrate (C-S-H) seeds on the strength development and reaction rate of PC/GGBFS binders cured at 0 °C were investigated. The results showed that the addition of C-S-H seeds can efficiently compensate for the strength loss caused by replacing PC with GGBFS, and this effect is more obvious at a lower GGBFS content (30%) than at a high content (50%). Better frost resistance was gained in the seeded binder containing 30% GGBFS than in the pure PC binder. The enhanced compressive strength and frost resistance in the seeded binary binder were attributed to the accelerated PC reaction rate, enhanced pozzolanic reaction rate and degree of GGBFS, and increased amount of pore-filling hydration products due to the nucleation effect of the C-S-H seeds.