Solidification of hypereutectic thin-walled ductile cast iron has been modelled in one dimension taking into account the precipitation of off-eutectic austenite dendrites during solidification. The simulations have been compared with casting experiments on plate geometries with plate thicknesses from 2.8 to 8.0 mm with good agreement for both cooling curves and nodule counts. The experimental results revealed that the eutectic solidification of plates with thicknesses less than 4.3 mm was characterised by two stages: (1) an initial arrest and (2) the main eutectic reaction. The initial arrest was associated with the discovered austenite dendrites in these plates. Moreover, the experimental results confirmed the numerical model’s prediction of off-eutectic austenite dendrites. The numerical model showed that the off-eutectic austenite dendrites mainly precipitate in the first stage before onset of the main eutectic solidification.