The Star Online news outlet reported, citing a court translator, that Vietnamese national Doan Thi Huong was released at around 07:15 a.m. on Friday (23:15 GMT on Thursday).
The outlet added that the woman was expected to return to Hanoi later in the day.
Doan Thi Huong, 30, was charged along with another suspected woman, Indonesian national Siti Aisyah, of poisoning Kim Jong-nam at Kuala Lumpur International Airport in February 2017 with the help of what investigators believed to be a VX nerve agent.
In March, Siti Aisyah was released after a Malaysian court dropped the charges against her.
While the prosecution insisted that the two women were well-trained assassins and knowingly sprayed the toxic agent into Kim's face, Aisyah and Doan pleaded not guilty and said that they believed they were a part of a prank for a reality TV show when they attacked Kim.