The Norwegian had given fair warning that he would light up German football, having scored 28 goals in 22 games for Salzburg in the first half of the 2019/20 season.
Before joining Dortmund in January 2020, Haaland had been on the scoresheet in eight group-stage games for the Austrian champions in the UEFA Champions League. This included a treble on his debut in the competition against Belgian side Genk, three goals in two games against Napoli and another against Liverpool at Anfield.
The son of former Leeds, Manchester City and Nottingham Forest midfielder Alf-Inge Haaland, the 19-year-old had previously made the headlines by scoring nine times in Norway's 12-0 win over Honduras at the FIFA U20 World Cup in May 2019.
"We can expect an ambitious, athletic and physical centre forward with a proven nose for goal," Dortmund sporting director Michael Zorc said of the player who would replace Paco Alcacer in attack.
Dortmund attacker Marco Reus, meanwhile, saw similarities with someone who had got 103 goals in 187 appearances for the club between 2010 and his departure for Bayern Munich in summer 2014.
"I don't think we've had that kind of striker since Robert Lewandowski," Reus told Sky Germany ahead of Haaland's first appearance. The new arrival talked a good game, too, which - we now know - is something he usually follows up on through his actions.
"I'm quite a direct player," Haaland told BVB TV at the club's winter training camp in Spain. "If I could choose, I'd just go straight towards the goal and score. That's what I do best."
Despite the hype surrounding his signing, most people were still expecting Haaland to take a little time to get up and running. Moving mid-season is never easy, and he would have to get used to the extra demands that come with both playing in the Bundesliga and at a club that had been crowned European champions in the past.
Dortmund were fourth in the table when Haaland landed in Germany, and their first game after the winter break would not stir up good memories. Augsburg had dealt a serious blow to BVB's title chance with a 2-1 home win the previous March, and they would prove inhospitable hosts once again.
The visitors found themselves trailing 2-1 shortly after half-time, and it looked like Florian Niederlechner would comfortably upstage Haaland when he made it 3-1 - and got his second goal of the game - on 55 minutes.
A minute later Lucien Favre went for broke by sending his new signing on in place of defender Lukasz Piszczek. The substitution would pay off in a matter of seconds.
Three minutes after his introduction, Haaland gave his side hope with a sweetly struck angled drive that went in off the post. Jadon Sancho levelled the game at 3-3 on 61 minutes, and then it was over to Haaland to complete the first of many astounding performances in black and yellow.
He tapped home a Thorgan Hazard pass to give Dortmund the lead on 70 minutes, and then - after 17-year-old Gio Reyna had also come on to make his first appearance - he raced through with 11 minutes to play to complete a remarkable 5-3 win for the visitors. Haaland had scored with his first three shots in German football, requiring only 10 touches to do so.
There were only 20 minutes between Haaland's first and third goals of a stunning debut, which ended with him taking the match ball home as the league's second-youngest hat-trick scorer and only the seventh to get a treble in his first game. He was also the first substitute to get three goals on debut.
"I came here to score goals - it's a good debut for me," the understated Man of the Matchday told bundesliga.com afterwards.
Favre hailed Haaland's impact as "incredible", all the more so given that the Norway international had been troubled by a knee injury in December and so wasn't even match fit.
Reus, meanwhile, correctly recalled that another former Dortmund No. 17 - Pierre-Emerick Aubameyang - had also hit three for Dortmund in an away win at Augsburg in August 2013. The Gabon international was the last player to score a hat-trick on his Bundesliga debut, eventually netting 141 goals in 213 games across all competitions before he left for Arsenal in January 2018.
"Erling trains incredibly hard," Reus said after the game. "I think the last guy to make his debut in Augsburg was Auba, and he scored three goals too. If it becomes the same kind of success story, I'd be all for that. Erling is making a good impression and he got off to a superb start today."
For Haaland, that's all it was. As if to prove that Augsburg wasn't a fluke, he scored twice more in each of his next two games against Cologne and Union Berlin.
He set a new league record in the process with seven goals in his first three matches, leaving fans and teammates alike in awe of his potential.
"The best thing about him is how hard he works every day," defender Mats Hummels said. "When you see that, you realise his performances are no accident. And that there's a very good chance he'll keep it up."
Haaland sure did.