The naked man was spotted outside his hotel on Chorlton Street, at about 04:30 BST.
Greater Manchester Police said it was a "genuine case of sleepwalking".
GMP tweeted: "We checked with officers; was proper somnambulism, not a dare. Person grateful for our help + saw the funny side themselves."
The man's identity has not been revealed by police.
A man was helped back to his hotel after sleepwalking into the street in Manchester city centre without any clothes on, police have said.