While a system which looks like a system of political residency similar to that of modern day ambassadorial plenipotentiaries had been developed by some kingdoms and empires that existed in early Yorubaland prior to the contacts with Europeans and which had served them well in several respect ranging from collection of toll revenue, protecting citizens of such empire and kingdoms to serving as embassies to these kingdoms and empires, yet this system eventually was responsible in some cases to the decline and eventual collapse of such kingdoms and empires. Why then did a system that worked so well to the growth of such empires and kingdoms eventually became its albatross by contributing to its fall? This study therefore examines the impacts of the system of Ajele as developed by the Old Oyo empire and later Ibadan hegemon in early pre-colonial Yorubaland and how this system contributed to the growth of these empires as well as their influence in the decline and eventual fall of such kingdoms and empires. In doing this, the study will make use of majorly secondary sources interpreting already existing materials on the subject matter. The study argues that while the system of Ajele in pre-colonial Yorubaland did well to ensure the growth of these kingdoms and empires yet there are important lessons from their histories that can be useful for contemporary African societies in the conduct of diplomatic relations.