Can you castle if your rook is under attack? Yes, you can — an attacked rook doesn’t automatically prevent castling. What actually matters is whether the king is in a position that satisfies the castling conditions; an opponent merely attacking your rook doesn’t, by itself, change that.

Why the Rook Being Attacked Doesn’t Stop Castling Under the FIDE Laws of Chess, castling is temporarily prevented only if your king is currently under attack, the square your king crosses is attacked, or the square your king moves to is attacked — plus the separate requirement that no pieces sit between the king and rook. Notice what isn’t on that list: the rook itself being attacked. So if your rook is under fire but your king satisfies every other castling condition, castling is still perfectly legal.

An Example Imagine you’re playing White and want to castle kingside. Your king is on e1, your rook is on h1, and the squares between them are clear. Now suppose Black has a piece attacking your rook on h1. If your king isn’t in check, f1 and g1 aren’t attacked, and neither the king nor the rook has moved before, you can still castle kingside — the attack on the rook simply doesn’t factor into the legality of the move.

What If the Rook Gets Captured? That’s genuinely different. If the rook is actually captured before you get to castle, you obviously can’t castle with it anymore, since the required rook is no longer there. The distinction is simple: rook under attack means castling can still be legal; rook already captured means castling with that rook is impossible.

The Common Confusion It’s easy to assume that because the rook is involved in castling, it must also need to be protected from attack. But FIDE’s castling restrictions are focused entirely on the king’s safety — the king can’t start in check, pass through an attacked square, or land on one. So if someone tells you “you can’t castle because your rook is attacked,” that statement simply isn’t correct under the actual FIDE Laws.

Yes, you can castle when your rook is under attack. Check the king’s position and the squares involved in the castling move — the rook being attacked is not, by itself, a reason to lose the right to castle.

Source: FIDE Laws of Chess, Article 3.8.2.1–3.8.2.2.