The 81-year-old was reappointed to head Fatah, the largest and oldest Palestinian movement, in a vote "by consensus," spokesperson Mahmud Abu al-Hija said at a news conference.
Since the death of long-time leader Yasser Arafat in 2004, Abbas has also headed the Palestinian Authority and the Palestine Liberation Organisation (PLO), the internationally recognised entity representing all Palestinians.
Palestinian president can revoke parliamentary immunity of opponents
Many analysts suggest Abbas will seek to use the five-day Fatah congress that opened Tuesday to strengthen his position and marginalise opponents.
He is unpopular with the Palestinian public - according to a recent poll, most Palestinians want him to resign - and faces challenges within his party.
His term as president of the Palestinian Authority, which began in January 2005, expired in 2009 but he remains in place as elections have not been held.
Divisions between Fatah, which controls the West Bank, and Islamist Hamas, which holds Gaza, remain deep.
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