An animal pen retention system includes a collapsible animal cage that has a plurality of walls. Each of the walls is hingedly coupled together. Thus, the collapsible animal cage is positionable in a deployed position having the collapsible animal cage forming an enclosed geometric shape. A plurality of clips is provided. Each of the clips is positionable on the walls when the collapsible animal cage is positioned in the deployed position. Thus, each of the clips inhibits the collapsible animal cage from being urged out of the deployed position.
