The solubility and crystallization behavior of ibuprofen was investigated in the presence of solvents (acetone and ethanol) and antisolvents (water and hydrogen peroxide). The solubility of ibuprofen was determined in the mixtures of acetone+water, acetone+hydrogen peroxide, ethanol+water, and ethanol+hydrogen peroxide. The phase boundaries of these ternary systems were determined as a function of the mixtures’ concentration at 27, 35, and 40℃. Based on the solubility data, ibuprofen was crystallized using the antisolvent crystallization technique. It was found that the external shape and internal structure of ibuprofen crystals were nearly independent of solvent and antisolvent, but the size distribution of the resulting particles changed. In the crystallization process, the application of ultrasound induced a significant reduction in particle size and caused severe agglomeration of micronized ibuprofen. This problem was solved by adding an external additive (Tween 80) to the solvent and antisolvent mixtures.