The 28-year-old was forced to miss his team's opening defeat to Brazil last week through suspension.
However, the forward now hopes that he can help the Croatians get a positive result against Cameroon in order to boost their chances of getting out of Group A.
"It is every player's dream to play at a world tournament. I'm eager to play, eager to prove myself together with my team," he told FIFA.com.
"I hope that my first appearance at a World Cup will be marked with a positive outcome. I am training very hard and this is maybe one of the most important matches. We are ready."
Mandzukic recently confirmed that he will be leaving Bayern Munich this summer.