The chest injury risk to a child occupant in a child restraint system (CRS) was investigated using Q3 dummy tests, finite element (FE) simulations (Q3 dummy and human models) and animal tests. The investigation was done for two types of CRSs (impact shield CRS and five‐point harness CRS), based on the UN R44 dynamic test. The tests using a Q3 dummy indicated that although the chest deflection in the impact shield was large, it was less than the injury threshold (40 mm). From the computational biomechanics simulations (using finite element FE analysis), it was predicted that the Q3 dummy chest is loaded by the shield and deforms appreciably under this load. On the other hand, the deformation of the shield was small. To clarify whether internal organ injuries due to chest compression can occur for an impact shield and a five‐point harness CRS, four experiments were performed using Tibetan miniature pigs with weights ranging from 11 kg to 13 kg. Severe internal organ injuries (lung contusion, coronary artery laceration, liver laceration) were found for the CSR with an impact shield. It is concluded that it is likely that the internal organ injuries without rib fractures could occur to child occupants sitting in the CRS equipped with an impact shield.