According to Genesis, God shuts Noah’s Ark after Noah and his family enter.
Genesis 7:16 says that those entering the Ark came in as God had commanded, and that the Lord shut Noah in. The wording places the final closing of the door in God’s action rather than describing Noah or one of his sons fastening it.
This moment marks the transition from preparation to the Flood itself. The text has already described Noah’s obedience, the entry of his family, and the animals coming into the Ark. Once the door is shut, the narrative moves to the rising waters and the destruction outside.
Popular retellings sometimes depict Noah closing a large wooden door himself, especially in illustrations and films. Genesis distinguishes between Noah’s responsibility to build and enter the Ark and God’s action in closing it. The verse does not name an angel or another assistant as the one who shuts the door.