This study aims to explore the extent of the efficacy of embassies as an institution of diplomacy in the political and foreign relations between nations in times of war and peace. In this respect, the Abbasid state proved how successful the embassies were in realizing its aims. The embassies proved successful in producing positive results which affected different issues of political and civilizing aspects. The study adopted the analytical method, applying the critical analysis of the different historical sources relating to the aims and objectives of these embassies. This gave a clear and an illuminating picture of the aims and significance of these embassies. The study consists of three chapters with a preface, introduction and conclusion. The preface gives a general survey of the political affairs of the Abbasid Caliphate during the period of study. The introduction examines some of the previous studies on the subject and gives an analysis of the primary sources which have been consulted. The first chapter deals with the diplomatic institutions which prevailed before the Abbasid era. The second chapter concentrates on the selection of ambassadors and their qualifications. It also describes the types of presents and souvenirs exchanged between Caliphs and Kings. The third chapter considers the different types of embassies discussing its aims and results. In conclusion, the researcher refers to a number of results of his study, the most important of which was that this historical era witnessed a considerable number of embassies with cultural aims which had a positive influence on civilization and progress.