The present invention relates to a pharmaceutical composition comprising brexpiprazole or a pharmaceutically acceptable salt thereof and at least one pharmaceutically acceptable excipient, wherein particle size of brexpiprazole or pharmaceutically acceptable salt thereof is D90 from about 10 μm to about 40 μm, particularly D90 is in the range from about 15 μm to about 30 μm and process of preparation of said pharmaceutical composition and its use for the adjunctive treatment of major depressive disorder (MDD) and treatment of schizophrenia.
