The fans, many perched on trees and traffic lights, sang, cheered and snapped pictures of the players with coach Jurgen Klopp calling the event "the biggest party ever".
"I had tears in my eyes," the coach told reporters after seeing the number of people who had come out to cheer for their seventh German league title win.
"We dreamed of something like this and when you look into the fans' faces, it is just amazing.
"This is the biggest party you could ever imagine," he added, a day after his team completed the season with a 3-1 win over Eintracht Frankfurt, having made sure of the title two weeks earlier.
Dressed in dark suits and ties, the players and coach, many wearing sun glasses after an all-night party on Saturday, displayed the trophy they had last won in 2002.
"I am so proud," said midfielder Kevin Grosskreutz, one of four Dortmund players to win a German call-up this season.
"No one can ever take this away from me. I was born here and I will always love this club," said the 22-year-old.
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