The Constitutional Era, as one of the prominent intellectual movements, played an important role in the political, social and cultural developments of this period. The main purpose of this research is to examine the foundations and external factors affecting nationalism during the Constitutional Era of Iran. It seems that external factors played an important role in the occurrence of the Constitutional Revolution and raising awareness among the people during this period. Our assumption is that external factors such as the expansion of the modern state before the Constitutional Era on a global level, Russia's defeat of Japan with an emphasis on the sense of Japanese nationalism, the introduction of the concept of nationalism into the Ottoman Empire, the nationalism of the peoples of the Balkan Peninsula, Arab nationalism and Turkish nationalism were among the first whispers of nationalism that could have a great impact on stimulating nationalism in Iran. The present research method is descriptive-analytical. The results and findings indicate that external factors such as the influence of great powers and their interventions, as well as global experiences, played an important role in stimulating people's awareness and social awakening. This set of factors led the masses of people to seek to build an ideal society.