The aim of this article is to propose a model to predict initial size and shape of CO2 bubbles leaked in shallow seawater from ocean CO2 storage. The volume of fluid (VOF) model in FLUENT was employed. The initial bubble sizes were predicted to increase with the increases in leakage velocity and leakage orifice diameter. The leaked bubbles were predicted to form into various shapes. A comparison of bubble shape predicted by the VOF model and observed from the recently published experimental data showed a reasonable agreement. It was found that the VOF method can be a reliable approach for predicting the initial size and the shape which are used to calculate a rising velocity and a dissolution rate of the bubble during the occurrence of the CO2 leakage in the ocean. © Universiti Malaysia Pahang, Malaysia.