Kim Jong-Nam Death: Malaysia Police Hold Female Suspect
Local police said that the woman was arrested at the airport in the capital Kuala Lumpur where Kim Jong-nam was targeted in an apparent poisoning on Monday.
She was in possession of a Vietnamese travel document.
Malaysian police say they are looking for "a few" other suspects.
Police said the arrested suspect, who was alone, was identified from CCTV footage taken at the airport. They named her as Doan Thi Huong, 28.
South Korean media have widely reported that two women, said to be North Korean agents, were involved and fled the airport in a taxi, though Malaysian police have not confirmed those details.
A grainy image broadcast in South Korea and Malaysia shows a woman wearing a white T-shirt with the letters "LOL" written on the front.
Malaysia is yet to formally confirm that the dead man is Kim Jong-nam, as he was travelling under a different name - Kim Chol. But the government of South Korea has said it is certain it is him.
Its spy agency is said to have told lawmakers they believe Mr Kim was poisoned.
Earlier, Malaysia state news agency Bernama reported that a woman from Myanmar was detained at the airport. It is unclear if that report was referring to the woman now under arrest.
If confirmed, it would be the most high-profile death linked to North Korea since Kim Jong-un's uncle, Chang Song-thaek, was executed in 2013.
North Korea has not commented on the death but officials from the country's Malaysian embassy have been visiting the hospital in Kuala Lumpur where Mr Kim's body has been taken.
Kim Jong-nam was attacked on Monday morning while waiting at the budget terminal of Kuala Lumpur International Airport for a 10:00 flight to Macau, Malaysian newspaper reports say, quoting police.
Exactly how the attack unfolded is still unclear. Officials and witnesses have variously said he was splashed with a chemical or had a cloth placed over his face. Earlier reports spoke of a "spray" being used or a needle.
He died on the way to hospital.