Qassim was a prominent Iraqi lawyer, civil servant, and publisher known for his advocacy for pluralism and democracy in Iraq. He was born in Mosul in 1914 to a widowed mother, raised by his two paternal spinster aunts, and showed promise early on. In 1931, at the age of seventeen, Yahya was accepted to the Baghdad Law Faculty, where he graduated at the top of his class in 1932. He subsequently became Assistant Executive Secretary to the Iraqi Cabinet and quickly rose through the ranks. He was promoted to the post of Executive Secretary to the Iraqi Cabinet at the age of twenty-one, essentially becoming the head of the Iraqi Civil Service. 

In 1945, Yahya Qassim launched the liberal Baghdad newspaper Al-Shaʿb [The People], where he served as editor from 1945–1958. In his editorials, he advocated for a pluralistic, democratic Iraq in which citizens, regardless of faith, should be considered fully equal under the law. In less than a year, al-ShaʿbAl-Shaʿbthe most widely circulated paper in Iraq and was known for its liberal editorial policy and non-partisan stance. True to Qassim's principles, several Jewish professionals worked alongside Muslims and Christians, both as journalists and in administrative positions. 

Despite being an Arab nationalist himself, Qassim strongly advocated for the equal treatment of Iraqi Jews, whom he believed were fully equal to Iraqis of other religions and beliefs and should be treated as such. He argued in his Al-Shaʿb editorials that the questions of Zionism as a political movement, the creation of the State of Israel, and the unquestionable full citizenship status and concomitant rights of Iraqi Jews were separate and distinct. Qassim made these arguments daily in direct opposition to Arab nationalist political groups and parties within Iraq. Additionally, Qassim provided legal counsel for the Jewish community and was part of the negotiating team for the denationalization law, which set the terms for Jews to leave Iraq between 1949–1952. 

Qassim continued to edit Al-Shaʿb until the July 14, 1958, coup d’état, which saw the newly installed dictatorial regime immediately ban it (the only newspaper banned due to its independent editorial policy) and confiscate its presses and infrastructure. Qassim was imprisoned for several months, followed by a period of house arrest, after which he decided to leave Iraq with his family to settle in Britain. 

In the 1960s and '70s, Qassim worked as a freelance writer and consultant at The Economist, The Economist Bulletin (published by the Economist Intelligence Unit), the Financial Times, The Christian Science Monitor, and the International Herald Tribune. In the 1980s, he started working on a book on the modern history of Iraq. Qassim passed away in his sleep during a short visit to the city of Curitiba, Brazil, in 2004. 

It is important to note the role Yahya Qassim played in the successful and lawful emigration of Iraqi Jewry to Israel and other parts of the world, under extremely difficult circumstances. He remained a champion of pluralism, democracy, and human rights throughout his life, and his legacy continues to inspire generations of Iraqis and others fighting for these values.