"This study is an attempt to understand better the development of Ottoman administrative structure and political culture by focusing on Celâlzâde Mustafa Çelebi’s (1490-1567) life, career and works. Celâlzâde Mustafa witnessed formation of Ottoman “classical” organization and culture during 16th century and he is accepted as one of the most influential author-bureaucrats during that time. His nickname “koca nişancı” which means old and great at the same time, indicates his venerated status among divan-i humayun scribes. He served for Ottoman chancery for more than 50 years; first as a scribe and private secretary of the grand vezir, then for 9 years as reisü’l-küttab and for 23 years as nişancı. Celâlzâde Mustafa contributed to the formation of Ottoman “classical” culture with his bureaucratic activities and works written on different subjects such as history, ethics, Ottoman law, religious studies and poetry."