Malaysian authorities had accused Doan Thi Huong of murdering Kim Jong Nam in early 2017 in Kuala Lumpur's airport by smearing VX nerve agent on his face.
But prosecutors agreed to reduce the charge from murder to "causing hurt by dangerous weapons" instead.
After Huong accepted the charge, the court sentenced her to three years and four months in prison including time already served.
Last month, prosecutors refused to grant Huong's request to drop the murder charge against her, despite dropping the same charge against her Indonesian co-defendant, Siti Aisyah.
That decision prompted the Vietnamese government to pressure Malaysia into releasing Huong.
TV prank
Both women had denied any intention to murder Kim Jong Nam. They said they were tricked by North Korean intelligence agents and thought they were carrying out a prank for a reality TV show.
Four North Koreans were also accused of involvement in the killing, but they fled Malaysia shortly after the incident.
Kim Jong Nam had been considered the heir apparent to North Korean leader Kim Jong Un before the two relatives became estranged.
