Micronization of ibuprofen using bottom-up process via rapid expansion of supercritical solution (RESS) were conducted to investigate its effects on formation of micronized ibuprofen. Physicochemical properties of processed ibuprofen were analyzed using XRD, DSC, FT-IR, SEM, laser diffractometer and dissolution testing. Effects of extraction pressure, extraction temperature and nozzle diameter on particle size were optimized using Taguchi’s orthogonal array and analyzed using analysis of variance (ANOVA). Processed ibuprofen retained its crystalline structure and has a similar chemical structure with unprocessed ibuprofen. The average particle size of ibuprofen was reduced from its original 48.549±2.304 μm into 3.765±0.024 μm under the optimum condition (T at 45oC, P at 200 bar and nozzle diameter at 200 μm). The processed ibuprofen showed an enhanced its dissolution rate by 1.79 times compare to unprocessed ibuprofen.