Sandwich composites with polymeric open-celled foams or honeycomb structures as core materials have been used widely in low-weight naval, aerospace and structural applications in the past. One major drawback of such foams is skin-core debonding. To overcome this, core materials with the same matrix as the skin are studied in this paper. Sandwich composites with fibre composite skins and a hollow glass particle-filled syntactic foam core are fabricated and tested under ballistic impact loading. Both the constituents have an epoxy matrix and are fabricated using a co-curing method which improves the skin-core debonding considerably. Parameters such as ballistic limit and energy absorbed by the samples are obtained for different core volume fractions and varying skin thicknesses. The effect of skin layup sequence has also been studied. It is found that samples with thicker back skins have better impact-resistant properties. The external and internal damage in the samples subject to different impact velocities is studied by visual means and CT scans. An energy-based analytical model is used to predict the ballistic limit of the samples, and to study the individual energy-absorption modes. The evolution of the contribution of the modes with time as well as the velocity profile of the projectile as it penetrates the composites are also obtained from the model. The experiments and the model show comparable ballistic limit results. © 2020 Informa UK Limited, trading as Taylor & Francis Group.