The goalkeeper acknowledged that Die Schwarzgelben's win at Eintracht-Stadion was anything but pretty and that Jurgen Klopp's men have much room for improvement
A double from Pierre-Emerick Aubameyang earned Die Schwarzgelben their first win in five Bundesliga games.
The result leaves Torsten Lieberknecht's men rooted to the bottom of the table, while BVB move into the top three, but the Dortmund goalkeeper acknowledged that they can play a lot better.
"It was a dirty victory, but we can build on the performance," the Germany international told his club's official website.
"We won, and that's the important thing. Braunschweig raised their performance with all their might in the defeat.
"We still have a lot to improve and have lapses of concentration when errors creep in. We have to work."
The game saw the return of defender Mats Hummels, who had not played since suffering an ankle injury back in November, and Weidenfeller stressed the importance of the Germany international to the club.
"He is very important. Mats is a crucial part of our team. With him we were able to play much better balls out from the back," he continued.
Weidenfeller also said that goalscorer Aubameyang has added another dimension to the Dortmund attack since his arrival from Saint-Etienne last summer.
"His pace and directness is very important to us. In the previous games, we have played too many crossfield balls," he argued.