A study was made on the formation of oil-ice sandwich, a phenomenon in which oil placed underneath an ice cover is entrappedi nice under freezingc onditions. The study was made as a part of a larger research project on the behaviour and recovery method of oil spilled in ice-covered waters. Laboratory tests were performed to study the ice growth under the oil layer. Numericalc alculation that takes into account the convective heat transfer through the oil layer agreed well with the experimental results. It was attempted to predict the formation of oil-ice sandwich in field conditions.