Dissatisfaction with the current government: The main cause of the revolution was a dissatisfaction with the government. At the time of the revolution there were around 30 million Muslims in Iran most of them were Shiites. The Shiites and working class did not support Mohammad Reza Shah Pahlavi's progressive and Western policies. Pahlavi Westernized the country and removed many age old traditions which sparked outcries and protests.
Social Political Repression: The Shah of Iran (a Persian monarch) acted similarly to many dictators. He suppressed any protests against him and dismissed their ideas. Iran did not have proper riot police, so the military always had to respond and usually ended up with casualties. SAVAK the Organization of Intelligence and National Security (the secret police) has also responded. Social support of the Shah diminished over the killing of protesters and protests increased.
Economic Division: Iran like many other Middle Eastern countries such as Saudi Arabia and the of Iraq are all oil countries. As Iran accumulated more wealth from its oil industry, a chasm opened between the oil families and the working class. As this chasm increased the working class protested against how there was such division and how the Shah did not do anything to help the problem.