A door is provided for a household pet carrier having a substantially parallelepiped box shape, with an opening on one of the sides of the box structure allowing the animal to enter and exit the carrier. Said opening can be closed reversibly by means of a door which prevents the animal inside from leaving the carrier. The door of the invention is essentially characterized in that it cannot be opened as in the case of similar known doors, with an opening having vertical-axis leaves, but rather by spreading apart the two leaves, of which it is made, in compass fashion, and said leaves, instead of becoming coplanar as in the closed position, assume a spread-apart position, with the hinge axis between the two leaves of the door being located, in this case, outside the container.