For the group matches against Australia, Serbia and Ghana, German fans have only bought 579, 655 and 682 tickets respectively, the DFB said.
"It is not only an issue of security, it is also the high cost for the trip and the accommodation," DFB chief Theo Zwanziger told reporters.
In total just over 25,000 Germans have ordered tickets for all 64 World Cup matches.
DFB general secretary Wolfgang Niersbach said he saw no cause for concern as the sales were very similar to those before the 2002 World Cup in South Korea and Japan.
"One should not be surprised if there is not the wave of arrivals that one would see if the tournament was held in Spain, Italy or England," Niersbach told the DFB website.
"Sales are normal and similar to the 2002 World Cup, and the comparison with 2002 offers itself because of the similar distance and the resulting costs," said Niersbach, who still expects vocal support at the June 11-July 11 event.
"Absolutely, because there is great interest for the team locally. But we should not compare it with the 2006 World Cup when Germany were hosts. Even for the 2002 final in Yokohama (between Brazil and Germany) we only sold 2,144 tickets to German fans," Niersbach said.
He said the cost of flying from Germany to South Africa to watch a single game was about 3,000 euros as offered by travel companies.
