With defending champions Bayern Munich, under new coach Pep Guardiola, having already enjoyed a 3-1 win at home to Borussia Mönchengladbach on Friday, 24-year-old Gabon forward Aubameyang showed why Dortmund paid French Cup winners St Etienne 13 million euros (US$17.3m) for him.
He opened his account by heading home a Marcel Schmelzer cross from the left wing to put Dortmund ahead after 24 minutes.
Aubameyang celebrated with his trademark forward somersault, then doubled Dortmund’s advantage when he slipped his marker and fired home across the goal on 66 minutes.
The Gabon star then converted a great pass from Robert Lewandowski on 79 minutes to wrap up his hat-trick before the Poland striker converted a penalty in the dying stages.
South Korea striker Heung-Min Son also scored on his first competitive appearance for Champions League side Bayer Leverkusen in their 3-1 win at home to Freiburg.
Germany striker Stefan Kießling put the hosts ahead with 22 minutes gone, but Freiburg’s new signing Mike Hanke levelled just before the break.
Son restored Leverkusen’s lead just two minutes after the break when he fired home from close range after a final pass from Sidney Sam.
Germany midfielder Sam then converted Kießling’s cross to seal the win with 52 minutes gone, while Leverkusen goalkeeper Bernd Leno protected his side’s lead when he saved a 67th-minute penalty from Jonathan Schmid.
Hertha Berlin marked their return to the top-flight after a year’s absence with a 6-1 rout of Eintracht Frankfurt.
Colombia striker Adrian Ramos and Tunisia forward Sami Allagui both scored twice in the hammering at Berlin’s Olympic Stadium while a first-half penalty from Eintracht Frankfurt midfielder Alex Meier was all the guests could muster.
Hanover 96 enjoyed a 2-0 win over Wolfsburg, who finished with nine men after both midfielder Maximilian Arnold and Swiss defender Timm Klose were sent off.
Arnold was shown a straight red card with just 32 minutes gone for a bad tackle on Hanover’s Tunisia defender Karim Haggui, while Klose was sent off seven minutes after the break for his second yellow card.
Hoffenheim were held to a 2-2 draw at home to Nürnberg. Newly-promoted Eintracht Braunschweig lost 0-1 to Werder Bremen in the evening game.