Ibn Sina (Avicenna) is primarily known for his philosophy and medicine, but there is almost no scientific discipline in which this great man didn't leave a significant mark. This paper gives a brief review of his contributions to medicine, especially to psychiatry. Medical works of Ibn Sina represent a pinnacle of most important medical achievements of his time. These works contain synthesis of all Greek, Indian and Iranian medical schools, but also new breakthroughs achieved by Muslim scholars through their own experimentation and practice. Although he wrote many medical works, his most important one is El-Kanun fit-tib, which can be translated as The Canon of Medicine. It's made out of five books which systematically show everything known in the area of medicine up until that point in time. In it, Ibn Sina discusses, among other things, the structure of psychological apparatus of human being and the connection of psychological functions with the brain as well as the role of psyche in etiology of somatic diseases. He also describes certain psychiatric diseases along with the explanation of their etiology and recommended therapy. He considered psychology to be very important for medicine, so in his psychological works he discusses, in great detail, the essence of human soul, consciousness, intellect and other psychological functions.