Rooney, one of England's most crucial players, had been in doubt for the Cup since breaking a bone in his foot in April.
Rooney visited a hospital in Manchester, England on Wednesday amid tight security for a crucial scan on the injury, and media sources later reported that he had been declared fit to be included in the England squad.
He was accompanied by England team doctor Leif Sward and David Davies, the Football Associatation's executive director.
Rooney later boarded a plane back to Baden-Baden in Germany, where the England's World Cup team is based.
Rooney's fractured a metatarsal bone in his right foot during a premiership match at Chelsea in April.
The striker's recuperation had been a source of intense interest and speculation by football fans and media alike, with one UK newspaper even dubbing Wednesday "Waynesday".
It had been hoped that, even if Rooney missed the first few games, he would be around for crucial later matches if his country qualifies.
The incident echoed the 2002 World Cup build-up, when David Beckham, the England captain, suffered a similar injury and was declared match fit with days to spare.
Sven Goran-Eriksson, the England coach, said earlier he remained hopeful that Rooney would be fit to play in the Cup.
"I'm confident he will take part in the World Cup and he is 300% confident that he will play," Eriksson said.