A statement on the Chessington World of Adventures' website said:
"Due to unforeseen circumstances, Chessington will be closed today.
"If you had tickets booked for today they will be valid for another day in the future."
More top news
The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The family of the police officer who was murdered in the Westminster attack have thanked those who were with him 'in his last moments'.