Mohammed Dahlan, who was head of the Fatah-dominated Preventive Security service in the Gaza Strip in the 1990s, and Jibril Rajub, the former Palestinian internal security chief, also joined the Central Committee.
"This is an unexpected result. It's a big change, a huge change," Naser al-Kidwa, the nephew of Yasser Arafat, the late Palestinian president and founder of Fatah, said.
Al-Kidwa also won a Central Committee seat.
Al Jazeera's Nour Odeh, reporting from Bethlehem, said the new additions will bring in a new approach.
"There will be some voices out there ... who would have liked other young faces to be included in the Central Committee," she said.
"Nonetheless, this is a strong Central Committee that is in agreement more or less on relations with Israel, on negotiations, and it's also a strong committee in terms of its position on Hamas and the Hamas takeover of Gaza."
But she said the election also brought surprises regarding the members of Fatah's "old guard" who were not elected.
"Namely, someone like Ahmed Qorei, one of the co-founders. [He is] somebody who has held a seat in the Central Committee for years. He is now out of the leadership position," our correspondent said.
Qorei, a former Palestinian prime minister and senior figure in negotiations with Israel, was among the party veterans who lost his seat.
Saeb Erekat, the chief Palestinian negotiator, hailed the success of the conference and the process of choosing new leaders after being elected to the committee on Tuesday.
"The Fatah movement has achieved an overwhelming success. It is not the success of those who have won, because everybody has, no one has lost. We are all winners," he told Al Jazeera.
Erekat said that the movement must now work towards Palestinian unity in order to make progress in the peace process with Israel.
"The Fatah movement's path is that of the Palestinian state," he said.
"We are a national liberation movement, we may disagree and we may agree, but our main goal is always the liberation of our land and the establishment of an independent state until we reach freedom and independence."
Delegates also voted for substantial change in the party assembly, known as the Revolutionary Council, where 80 posts were up for grabs.
The results of the elections were delayed by problems in collecting the votes of the 300 delegates who the rival Hamas movement prevented from leaving the Gaza Strip.
The count was postponed twice to allow more time to collect the Gaza ballots.
Abbas himself was re-elected as the Fatah leader on Saturday. He was the only candidate and was endorsed through a show of hands. The Palestinian president also sits on the Central Committee.
About 2,000 Fatah members began meeting for what had been billed as a three-day conference last Tuesday, but with much debate over a new political programme and changes to the party leadership it had dragged on for a week.
Many delegates had hoped that the conference, the first for 20 years and the first on Palestinian soil, would revitalise Fatah's ageing leadership, which has been harmed by allegations of corruption and cronyism.
In his opening speech on August 4, Abbas acknowledged a number of errors he said that Fatah had committed, urging delegates to learn from them and use the conference as a platform to give Fatah a new start.