The aim of this study was to produce niflumic acid nanoparticles without using an organic solvent, in order to achieve an increased rate of dissolution of the final products. Co-grinding with excipients was used to decrease the particle size. Poloxamer 188 (P) and mannitol (M) applied as co-grinding materials stabilized the system, preventing aggregation of the nanocrystals. The morphology and particle size distribution of the products were visualized by using scanning electron microscopy and laser diffraction. The crystalline states of the samples were investigated by differential scanning calorimetry and X-ray powder diffraction. The rate of dissolution of niflumic acid was measured with a paddle method from simulated media. It was concluded that the particles produced were in the nanometer range (the mean particle size was ~250 nm) and the nanoparticles maintained their crystallinity during the process. The rate of dissolution of the coground sample was significantly improved.