The effectiveness of two oil fences deployed in tandem to maximize the containment of oil is investigated. To assess the effectiveness of the tandem fences, the viscous flow field around the fences in tandem are analyzed numerically. Then, the trajectories of oil droplets which escaped beneath the fore fence are computed applying the Lagrangian particle-tracking method, to check under what conditions the droplet can be contained between the tandem fences. The validity of the calculated trajectories is checked experimentally by using spherical beads made of paraffin and droplets of kerosene, and the model fence of draft of 4 cm. The numerically predicted trajectories of the droplets show fairly good agreement with the experimental results. The method is applied to predict the motion of the weathered oil. It is shown, numerically, that most of the leaked oil can be trapped between tandem fences, when the distance between the fences is about 10 times the draft of the fore fence.