The present study aims at investigating the life of high-rank philosopher and theosophist, Haj Mulla Hadi Sabzewari and explaining his scientific life. The main question of the study is as follows: “How was Mulla Hadis’s scientific activity, and how much was this mystic-philosopher’s role in advancing philosophy and theosophy?” This study deals with other subsidiary questions as well. Besides, in this study, we have stated Hakim Sabzewari’s role in explanation of Mulla Sadra’s thoughts. The research method was using library resources. And among the findings is that Hakim Sabzewari was the best-known philosopher in 13th century, and that his fame was due to his exposition of Mulla Sadra’s thoughts and ideas, clarifying its complications in a way that – as some philosophers have pointed out – no one has exposited Mulla Sadra’s thoughts better than he has. This is quite clear in his invaluable works