The article examines the professional development of secondary school principals in Nigeria. Drawing from vast review of literature on professional development and appointment of school principals in other countries, the article canvasses the position that secondary schools in Nigeria should be administered by skilled personnel who have the appropriate training and competencies for school management and leadership, rather than the present practice of using years of teaching experience as a major yardstick for the appointment of principals. It advocates systematic professional development programmes for prospective and practicing school principals, and concludes that professional development of principals is a means to maintain and enhance the effectiveness of secondary school administration in Nigeria.