The 17-year-old Pulisic, who played the entire 90 minutes for the first time in seven Bundesliga appearances, is the fourth youngest player to score in a Bundesliga match.
The youngest player to score is Dortmund
teammate and mentor Nuri Sahin, who plays for Turkey but was born and raised in Germany.
"It's unbelievable," Pulisic said on Sky after the game. "I am at a loss for words, can't really explain it."
Pulisic's goal in the 38th minute followed a short corner that was played to Mats Hummels, who laid the ball off to Pulisic, who slotted it inside the near post.
The game marked Pulisic's first home start at the Westfalenstadion. Dortmund was playing three days after its crushing 4-3 loss to Liverpool in the second leg of its Europa League quarterfinal series. Dortmund's next match is Wednesday against Hertha Berlin in the German Cup semifinals.
"We've got many good players," Pulisic said of the competition for playing time. "I can't make any claims. I am just happy about every minute I can be on the field."