The Frank-Kasper phases were already known in 1982 when quasicrystals have been discovered but their complex architectures are now considered as making a link between simple close-packed periodic structures and some quasiperiodic ones. These tetrahedrally close packed structures are observed in many materials from elements to intermetallics as well as self-assembled soft materials like micellar systems, den-dritric liquid crystals, star polymers and more recently block-copolymers or heated gold nanocrystal superlattices. We report here the existence of a Frank-Kasper phase with hexagonal symmetry (MgZn 2 type, also labelled C14) in superlattices of monodis-perse hydrophobically-coated gold particles at room temperature obtained from sus-pensions in various solvents. The existence of such a structure in this system is analysed in terms of geometrical parameters including gold core diameter, ligand length and grafting density and an energetic approach based on van der Waals attraction. Hydrophobically-coated gold nanoparticles is a new system that exhibit a Frank and Kasper phase built by one-size objects. This result opens a route towards nanoparticle superlattice with complex structures and thus original physical properties.