It was actually visiting Sepsi who took the lead when Vosmin Matei's free kick went all the way into Djurgården's goal.
But Djurgården woke up quickly and equalized just four minutes later.
Piotr Johansson found Hampus Finndell after a pattern attack.
Already in the 23rd minute, the Stockholm team had turned around when a Joel Asoro in great form headed in 2-1.
- We get off to a rough start, the first ten minutes.
Then when we score the goal (1-1), I think the whole match changes, says Joel Asoro to Sportbladet Play.
With 20 minutes left to play, Asoro showed class again.
He tricked a Sepsi defender and shot neatly to make it 3-1.
The goal was the striker's fourth in the doubleheader.
The victory and the promotion still came with a little smolk in the cup of joy as the important midfielder Rasmus Schüller was forced to change with a bandaged left thigh.
Emmanuel Banda replaced the Finn who was also a question mark before the match due to a thigh problem.
During the break they also had to replace Finndell.
Djurgården will now face Apoel FC from Cyprus in the playoffs.
Those matches are played on August 18 and 25 and Dif ends at home.