Suha Arafat, speaking to CNN from Doha, Qatar, did not say who she believed killed her husband. She identified his killers only as "they."
"I'm convinced it was a political murder, a political assassination," she said. "They wanted to get rid of him."
Arafat died in November 2004 in a Paris hospital. He had been transferred there after becoming sick during a meeting in the Palestinian Authority more than two weeks earlier.
Al-Jazeera released a report Wednesday that said Swiss researchers say Arafat might have died from polonium poisoning. But the scientists said at a news conference Thursday their findings were not definitive, CNN said.
"Was polonium the cause of death? Our study has not been able to prove categorically a hypothesis of poisoning or another of non-poisoning by polonium," said Francois Bouchud, director of Lausanne University Hospital's Institute of Radiation Physics.
Polonium, a highly radioactive element, is lethal even in small amounts. Alexander Litvinenko, a former KGB agent living in London, was killed by polonium in 2006.
Wasel Abu Yousef, a leader in the Palestinian Liberation Organization, blamed Israel. Arafat was one of the major leaders of the Palestinian fight against Israel for decades before opening negotiations that led to the 1994 Oslo Accords.
Yigal Palmar, a spokesman for the Israeli Foreign Ministry, called the accusation "utter nonsense."