The 20-year-old forward from Norway scored twice at Sevilla and trails only Mbappe as the player with the most Champions League goals before his 21st birthday, with 18 goals in 13 matches. Mbappe, 22, scored 19 goals before turning 21.
Mbappe made a splash against Barcelona in Tuesday's 4-1 win with his three-goal performance, which Haaland pointed to as a source of motivation.
"When I saw Mbappe score the hat trick, I got free motivation, so thanks to him," Haaland said after the match. "He scored some nice goals and I got a free boost from him, so it was nice."
Sevilla took an early lead thanks to Suso, but Mahmoud Dahoud equalised it in the 19th minute. Haaland put Dortmund ahead in the 27th from inside the area after a nice give-and-go exchange of passes with Jadon Sancho, then added to the lead in the 43rd from close range after a fast breakaway. Luuk de Jong scored a late goal for Sevilla.
"We had a good plan,'' Haaland said. "[Borussia manager] Edin [Terzic] has been good and I've been talking a lot with him. He said today would be my game and that I would get my chances and I did, so it was an important win.
"It was not good to let in two goals, but it is good to score three away goals and take them with us.''
Like Mbappe, Haaland has been linked to a move to Real Madrid, among other clubs. When asked about his thoughts on the Spanish club, Haaland demurred by saying "it's nice to be wanted."
On the rumours of a potential exit from PSG, Mbappe said after the Barcelona match: "I have always said that I am happy here. This sort of match makes me even happier. The PSG shirt is one that I hold dear to my heart."