In this article, the interaction between a methane molecule and a graphene plane in liquid water has been characterized employing DFT-based free energy Molecular Dynamics calculations. This system represents a good model to understand the generic interaction between a small hydrophobic solute (methane molecule) and an extense hydrophobic surface (graphene plane). The structural and dynamical properties of graphene and methane hydration water are analyzed and found to be closely related to the main features of the potential of mean force. The results could be used in coarse-grained models to take into account the effect of the hydrophobic interaction in realistic systems relevant to experiment.