We demonstrate the pressure-induced formation of supercrystals made from PEGylated gold nanorods (NRs) in aqueous suspension. Utilizing the combined effect of hydrostatic pressure and salt on the solubility of the organic poly(ethylene glycol) (PEG) shell that passivates the NRs, the reversible formation of two-dimensional hexagonal supercrystals has been observed by means of small-angle X-ray scattering. The pressure dependence of the crystal lattice’s structural parameters is determined. By time-resolved measurements performed after a pressure jump, the growth process of the crystals is found to be completed already after a few seconds. The presented results demonstrate that by PEGylating nanoparticles, pressure-induced homogeneous supercrystals can be formed for different particle shapes, in particular, anisotropic NRs, which determine the resulting lattice type.