The Belgian defender was named on the bench for last weekend’s draw with Tottenham and has trained all week without suffering any adverse reaction.
Guardiola says he is ready to play from the start, as is Gabriel Jesus, who delivered an impressive cameo on his debut against Spurs.
"Kompany is fit,” Guardiola said. “We will see tomorrow but he’s fit, he's ready.
"Last game he was on the bench which means he’s fit otherwise he would not have been there. When they are on the bench it’s because they can start.
“Gabriel is fit, not injured. He’s already three weeks with us. He is fit and in shape. We will see tomorrow [who will play].”
City travel to London looking to make it the fifth round of the competition having already beaten Palace at Selhurst Park in the league meeting between the two sides in November.
He says City’s display that day was arguably their worst of the season - and he expects another difficult test on Saturday.
“It was a really tough game,” he said. “It was one of the worst games that we played this season but we won and when that happens everything is perfect, but we didn't play good.
“We expect a tough game in the FA Cup. Every game is complicated, so it will be tough - the stadium, Palace’s situation, because it’s away."