The Theatre was constructed under the patronage of Agrippa, son-in-law of Augustus, between the years 16 and 15 BC, when the Colony was promoted as the provincial capital of Lusitania. Like the adjacent Amphitheatre building, the Theatre was built partly on the slope of a hill, something which substantially lowered the costs of its stonework. The rest was built of concrete lined with ashlar masonry.

Although the Romans were not very fond of the theatre, a city of prestige could not go without a building for the theatrical games. The one at Emerita Augusta was especially generous in terms of its capacity: approximately six thousand spectators. The spectators were distributed from the bottom to the top in accordance with their social rank, being divided over three sections of stands: the summa cavea, media cavea, and ima cavea – all of which were separated by corridors and barriers. All stands were accessed with ease by means of small staircases distributed radially around the caveas. Through hallways, it was possible to get to the access doors, or vomitoria.

The deteriorated upper grandstand, or summa cavea, was the only one that emerged from the building before the beginning of excavation in 1910. As the vaults of the entrances were ruined ages before, only the seven bodies of the grandstands were left standing, giving rise to the people of Mérida baptizing these ruins as the "Siete Sillas" (Seven Chairs).

The ima cavea, where the gentlemen of the city sat, was modified in Trajan's time – with a sacred space surrounded by a marble railing being erected in its center. In front of the ima cavea, three wider and lower stands can be seen where the judges and priests of the city enjoyed the show seated on movable chairs. They accessed their seats from the large side doors located at both ends. Atop said doors were the stands of the judges who sponsored the show.

The semicircular space where the choir was located, the orchestra, has a floor made of marble that is the from a later renovation. Behind the orchestra rises the wall of the proscenium, made with circular and rectangular exedras. The stage unfolded around this space. Originally, it was a wooden platform under which all the machinery for the theatrical rigging system was hidden.

The stage was closed off with a wall that measured thirty feet in height, the scaenae frons, structured in two bodies of columns between which the statues of deified emperors and gods of the underworld can be seen. Everything sits atop a podium decorated with luxurious marble. The scaenae frons has three openings that actors used to enter the stage. The central one, the valva regia, is topped with a lintel on which the seated statue of the goddess Ceres rests (or Livia, the wife of Augustus, deified). From the crown of the scaenae frons, a wooden canopy probably was hung to improve the acoustics of the venue, which were already excellent.

Behind the wall of the scaenae frons there was a large porticoed garden enclosed by walls with niches that were decorated with statues of members of the Imperial family. Along the axis of this portico, in line with the valva regia and the sacred space of the ima cavea, is the aula sacra holy space – a small, sacred space with an altar table where the figure of the Divine Augustus was honored.

The Theatre's House-Basilica

At the west end of the Theatre's portico, the Theatre's House-Basilica can be seen, a dwelling whose excavating archaeologist, José Ramón Mélida, believed that the rooms that had apses with windows were part of a church where one of the first Christian communities met, hence the "House-Basilica" name.

The house's entrance is to the west and faces a road made with flat slabs of diorite which runs from east to west. The dwelling's fauces led to series of rooms that were organized around a porticoed courtyard in whose center the remains of a pond can still be seen. Some rooms still conserve the remains of mosaics decorated with geometric and plant themes.

Behind the courtyard are the apsed rooms, which invade areas that previously formed part of the Theatre's portico. The rooms were probably covered by a barrel vault and they were probably finished off at the apses with a semi-spherical cap. The parts of the walls (plastered with paintings) that remain are decorated with imitation inlaid marble on the plinths and, in the area of the apse, atop pedestals, remain the lower third of the some characters, perhaps some servants, dressed in colored tunics and decorated with brocade fabric.

Apart from the floor of the apse area, which was possibly covered in marble, the rest of the room was decorated with a mosaic that highlights the presence of a krater inscribed in a square.