The "Room of the Theatrical Masks" is a rectangular chamber located at the southernmost part of the complex. It is covered by a segmental barrel vault that, though extensively restored, still bears a few fragments of its original painted decoration. The southern wall is pierced by an opening that leads to a currently unexplored portion of the domus.
The paintings that grace the walls display vegetal ornaments in abundance: thin strings of banches and leaves in the lunettes and slender garlands across the side panels. Inside the main panels, figures belonging to the Dionysiac realm are suspended in front of the solid background. Among them is easily discernible a dancing Pan that carries a tyrsus and a pine cone.

Tragic masks and tambourines (tympana), painted on the middle panels of the north wall, evoke theatrical atmospheres and rituals in honor of Dionysos. In spite of the overall "flatness" of the painted decorations, there are some attempts at perspective rendering (see, for example, the masks that partially overlap the tamburines).

The atmosphere of sacredness is reinforced by the representations of flying swans with fillets in their beaks and a centuar, of which only the torso now remains.

On the south wall remnants of a previous decorative phase is visible in those areas were the stucco had fallen off; the surface was roughly picked to increase the bounding of the new layer.

The face of a Gorgon – brightly painted in yellow, red, and black – is framed by a mane of disheveled hair, behind which black snakes emerge. Two large red wings are spreading behind her.
Two symmetrical niches flank the central opening of the northern wall – they seem to have contained implements used in domestic rituals.

A geometric black on white mosaic, composed of a perimetral frame encircling a diamond and semi-diamond pattern, decorates the floor. A narrow canal, cut into the ground in a later phase and covered with re-used marble slabs, crosses the room in a north-south direction.