The Iranian Constitutional Revolution (1906-1911) was a complex sociopolitical movement that various ideologies supported. By 1906/7 Constitutionalists established a parliament and drafted a constitution that relied on the Shiite clerics’ participation. However, despite the clergy’s agreement on the Revolution’s initial plans that included modern ideas that Iranians had imported from Europe, the group soon fell into disagreement and a bitter fight ensued. The schism eventually turned violent that led to the killing of some notable clerics from both sides. Mullah Muhammad Kazim Khurasani (1839-1911) and Shaykh Fazlullah Nuri (1843-1909) were two of the famous clerics that at first supported Constitutionalism. Khurasani came from a humble upbringing and Nuri with his affluent background had close ties to the Iranian monarchy. Both had studied Shiite jurisprudence (fiqh) under one prestigious master (Mirza Hasan Shirazi) at Najaf. Khurasani became the rector of Najaf’s seminary and eventually the Shiite world’s highest-ranking Source of Imitation (marja’), while Nuri chose to return to Tehran and became a leading religious figure in the Iranian capital. Nuri first sided with Constitutionalists but suddenly changed his mind and openly opposed Khurasani. Nuri viewed secular civil codes, which the Constitution guaranteed, as un-Islamic. He objected to a long list of goals of the Constitutionalists, which included establishment of schools for women and equal rights for all Iranians. But Khurasani not only did not object to any of that, he used a rational approach to support what he thought Iran desperately needed which was a representative legislative body and laws that protected everyone. Consequent to that belief Khurasani issued several statements claiming anyone who objected to Constitutionalism was an infidel (kafir) and thus should be dealt with accordingly. Khurasani sources used for this study include his religious decrees, statements, and letters to different entities including the parliament expressing his support of that institution in addition to contemporary accounts and newspapers of the early 1900s. Nuri’s sources include his nightly bulletin that he published and paid for personally while protesting the establishment of the parliament in his sermons and contemporary accounts that were published in newspapers at the time. Through careful examination, comparison, and juxtaposition of these sources, this study suggests that Nuri became an anti-Constitutionalist since he thought the constitution would undermine clerical power in Iran and also negatively affect his wealth that he now had to pay taxes for.