Abstract: Yahya Ibn Adi was among Christian scholars who especially distinguished themselves in the 10/11th century in Baghdad. He was no longer relying on the caliphs but found his own means of living which in turn prolonged his own academic interest. Consequently, he was no mere translator any more but genuine scholar. He was not only the leader of his group but was also dubbed as the best Christian translator, logician and theologian of his times. This is justified, in addition, by his ample productivity in those fields of enquiry. A considerable number of such works have evidently been used by contemporary and later writers and have also reached us today. Hence, researchers consider that it is in these aspects that his distinctive contributions to scholarship lie and therefore he deserves more serious study. The present study discusses Yahya Ibn Adis theory of happiness (al-Saadah) as reflected in his major work on ethics, Tahdhib al-Akhlaq (The refinement of character). It confines itself to discussing the concept of happiness and to finding out the answer to those particular questions regarding its nature such as what is meant by happiness or what does happiness consist of? Why is happiness the end to be achieved by man and for which sake he was created? Is happiness attainable in this life or the next? Who is the happy man? and so forth.