Neymar, 34, has not played for Brazil in their first two games due to a calf injury as concerns grew this week that he may miss the entire Group stage.
Their final clash comes against Scotland as the two sides meet almost three decades on from their last World Cup clash in 1998 when the South American side claimed a 2-1 victory en route to reaching the final.
As the clash draws near, Ancelotti has revealed that Neymar will be okay to play as the Selecao aim to book their place in the next round.
"He is available, he trained very well this week, he is fit and able and ready to play. We are very happy that he is back, he is a high-quality player.
"He can play half the time or the whole 90 minutes. He is very well, he worked very, hard so he is ready. His attitude is very good, he is in very good spirits, he's a good player and teammate, he's very serious and we want to put him back to play as soon as possible. He brings experience and knowledge, he is doing very well."
Brazil secured their first victory at the 2026 World Cup last Saturday by defeating Haiti 3-0 in a performance that Ancelotti claimed was “complete” after the final whistle.
Brazil’s last three defeats in the group stage at a World Cup have all been suffered on matchday three in what might be a worry for Ancelotti as he finally hands Neymar a chance.