In 1955 he joined the Arab Nationalist Movement (ANM), and two years later was arrested by the Jordanian authorities for his political activities.

In September 1999 he returned to the West Bank under a deal struck between Yasser Arafat and Israel's Prime Minister, Ehud Barak.

Israel held Mustafa personally responsible for 10 different car-bomb attacks undertaken by the PFLP during his time as general secretary (in Jerusalem, Or Yehuda, Yehud, and Haifa) and other shootings.

Associated Press said, "Marching in the Ramallah funeral procession were the leaders of Palestinian factions that have been riven by rivalries in the past".

"[8] Israeli tourist minister Rehavam Ze'evi, leader of the far-right nationalist Moledet party, was subsequently assassinated on 17 October 2001 by PFLP member Hamdi Quran in revenge for Israel's killing of Mustafa's.