The Chelsea defender played his part in yesterday's 1-0 victory over Joachim Low's men in Port Elizabeth as the Serbs rekindled their hopes of making it to the Round of 16.
A 1-0 defeat by Ghana in their opening Group D game had left them facing an uphill task in South Africa, but they responded superbly as 10-man Germany floundered in the wake of Miroslav Klose's first-half dismissal.
However, Ivanovic knows their heroics at the Nelson Mandela Bay Stadium will count for little if they do not turn in a similar performance against Australia in Nelspruit on Wednesday.
Ivanovic said: "It's given us back the respect that we lost in the first game. But we have not finished. We must perform, we must stay compact, we must stay strong in our third game. We must now start thinking of the third game against Australia.
"In this game, we showed character and we will just try to do our best on the pitch.
"Everyone is happy now at the moment and there's a great feeling - but we are not qualified. We just have three points and we need to keep the same focus for the third game."
Apart from striker Milan Jovanovic who scored the game's only goal, Serbia also had keeper Vladimir Stojkovic to thank when he saved a 60th-minute Lukas Podolski penalty after Nemanja Vidic had inexplicably handled inside the box.
The Manchester United defender was a relieved man, but his thoughts quickly turned to the clash with the Socceroos.
"I have played against a few of their players in England - Lucas Neill, Tim Cahill, Brett Emerton - and I have a big respect for their team. Physically, it will be a difficult game," said Vidic.
"Our people will be satisfied after we won this game, and that's the most important thing. If we get to the second round, they will be very, very happy."
For the Germans, who cruised past Australia in their opening game, defeat came as a wake-up call and one which is unlikely to go unheeded.
Defender Per Mertesacker said: "We must approach the game against Ghana as a cup final. It is an absolute must-win game for us."
Low was philosophical in defeat, but leapt to the defence of youngsters Holger Badstuber and Thomas Mueller, who performed well against Australia, when asked if it had been a game too far for them.
He said: "I don't think they were over-taxed, I don't think it was too tall an order for them. Badstuber didn't defend particularly well for the goal, but Krasic is a great international player and you can't always counter such attacks."