The Ivory Coast striker converted a penalty in the 81st minute and celebrated with hugs from his teammates. The second goal in the 86th came off a cross, and the third in the 88th after a corner. The hat trick spanned 7 minutes, 32 seconds.
Dortmund won 6-0 in a game which lasted 109 minutes rather than the standard 90 to give more players time on the field. The game against Swiss club Basel was part of Dortmund’s winter training camp in Spain before the Bundesliga resumes next week.
The goals marked Haller’s first for Dortmund. He was diagnosed with a testicular tumor in July, less than two weeks after joining Dortmund as a replacement for Erling Haaland, who was sold to Manchester City.
Haller’s return to the field came on Tuesday as a substitute in a 5-1 friendly win over Fortuna Düsseldorf.
The French-born Haller led the Dutch league last season with 21 goals, and he scored 11 more during Ajax’s run to the round of 16 in the Champions League. Without him, and following a spate of injuries, Dortmund have struggled in the Bundesliga and are in sixth place, nine points off leaders Bayern Munich.