The incident happened around 9 p.m. on the Metro Expo line platform near South Flower Street and West Jefferson Boulevard, according to Los Angeles police.
Police said the victim was stabbed while standing on the platform and waiting for a train.
The victim was transported to an area hospital in stable condition. Meantime, a long trail of blood was left from end-to-end on the train station platform.
Detailed information on the victim and suspect was not immediately released.