Muhsin Ibrahim was born in Ansar in southern Lebanon in 1935. Ibrahim worked as a school teacher in southern Lebanon. He joined the Arab Nationalist Movement in the 1950s, being a fierce supporter of the Egyptian president Gamal Abdel Nasser. He took part in the first conference of the Arab Nationalist Movement in Amman on December 25, 1956, and was elected to the leadership of the organization. In 1964, Ibrahim took part in meeting with Nasser, as the Arab Nationalist Movement tried to convince him to support the Dhofar Rebellion. In early 1966, Ibrahim travelled to Taiz along with George Habbash and Hani al-Hindi, as an delegation of the Arab Nationalist Movement seeking to convince the Yemeni National Liberation Front to merge with the Front for the Liberation of Occupied South Yemen.