The Europeans took an early lead through Aladje, who found the back of the net following a corner in just the third minute of the game.
Portugal continued to have the majority of the chances in the first half, forcing Korean goalkeeper Lee Changgeun to make a series of saves.
However, South Korea were able to level just before the half-time whistle following a counter-attack that gave Ryu Seungwoo a clear shot at goal.
Bruma restored Portugal's lead in the 60th minute, finding the target at the second time of asking, having seen his first effort stopped by the keeper, but Kim Hyun pulled the Asian side level again 16 minutes later.
Both sides had chances to score a winner inside the last 15 minutes, but neither were able to find the target.
The result leaves Portugal at the top of Group B on goal difference.