Hybrid Monte Carlo and classical molecular dynamics simulations of a hydrated 2,4,6-trichlorophenol bilayer are presented. In line with recent freeze-fracture electron microscopy observations, the present investigation confirms that 2,4,6-trichlorophenol can form stable, lamellar structures. Self-assembly into a bilayer arises from strong dispersion forces that favor stacked arrangements of the monomers, as is demonstrated by high-level quantum chemical calculations. It also results from the subtle balance between hydrophobic and hydrophilic contributions, responsible for the preferential orientation of the aromatic compounds and the cohesion of the supramolecular arrangement. Imbalance of these contributions is illustrated in the case of 2,6-dichlorophenol that does not yield lamellar structures.