Former European champions Dortmund, who beat Real at home in the group stage earlier this season, reached the last four for the first time in 15 years when they beat Malaga with two last-gasp goals in one of the competition's biggest comebacks.
With an undisclosed number of tickets available on open sale on Tuesday, Dortmund were surprised by the number of people determined to sit it out and get their hands on one. There were also minor scuffles during the vigil.
"Dortmund fans are passionate, emotional and this club is marked by something unusual," said Daniel Schrader, who spent two nights waiting for the ticket counters to open.
Dortmund did not say how many tickets eventually went on sale but with each fan able to purchase two tickets, many supporters camping in front of the offices left empty-handed.
"We underestimated the run on the tickets," club CEO Hans-Joachim Watzke said in a statement. "We will draw our lessons and will not have a free sale like this again."
With around 80,000 spectators per game, Dortmund have the second highest average attendance in Europe behind Barcelona.
Their stadium capacity, however, is reduced to 65,000 for European matches that do not allow for standing areas, unlike the Bundesliga.
Schrader, who arrived on Sunday afternoon, was among the first to get his tickets after having to wait another 15 minutes at the counter with the club's computer system crashing under the weight of online requests.
"I have been waiting since Sunday afternoon for these two small pieces of paper," a beaming Schrader said. "We battled through for two days. It was tough but it was all worth it now."
