This paper aims to provide a descriptive-analytical framework for Islamic Republic of Iran's public diplomacy and review this issue in Lebanon, in particular. Public diplomacy includes wide range of activities, therefor, it has different definitions, but generally it is the efforts of one government or state to make a favorable image of its policies and goals in minds and thoughts of the elites and ordinary people of another countries. The difference of this issue with public relations and propaganda is the mutual communication that takes place through bilateral dialogue and persuasion.This article, citing to American Institute Zogby’s poll, and with this question that what are the main reasons for the success of Iran's public diplomacy in Lebanon, is seeking to prove the hypothesis that this success is due to several things: its reliance on governmental and civil networks in this country, Lebanese positive historical mentality toward Iran, and also presence of Shiite and Hezbollah, as a non-operator, and non-governmental agent in Lebanon.