A modular animal pen system comprises front and rear panels and opposed sidepanelsextending between the front and rear panels to form a primary enclosure. Thefront panel hasadjacent doorway apertures formed therein to receive respective selectivelyclosable gates,and a mullion is disposed between the doorway apertures. The mullion has afirst slot, and asecond slot in the rear panel is in registration with the first slot. Theanimal pen systemfurther comprises a removable divider panel whose longitudinal ends are sizedto fitremovably within the respective slots so that the divider panel can divide theprimaryenclosure into two secondary enclosures. The side and divider panels may beformed byinterchangeable profile panels, and the front and rear panels may be formed byinterchangeable face panels connectable end-to-end to form a junction slottherebetween sizedto receive the longitudinal ends of the profile panels.
