We introduce a high-pressure cell for fluorescence fluctuation spectroscopy. The pressure cell consists of a cylindrical, fused silica microcapillary and a modified pressure plug, which connects the cell to a pressure generating apparatus. The capillary serves both as the body and the optical window of the cell. The pressure cell is mounted onto the stage of an optical microscope. The small diameter of the capillary allows the use of high numerical aperture objectives, which are required for fluorescence fluctuation experiments. The pressure stability of the cell has been tested up to 4 kbar. We performed two-photon excitation experiments on simple dyes as a function of pressure. The diffusion coefficient was determined by fluorescence correlation spectroscopy. We also used the same cell to measure the pressure dependence of fluorescence lifetimes.