The city of Carmona in the 14th century acted as the Square of Seville and had three fortified Alcázares plus a grated perimeter surrounding the entire urban town. These were the Abajo alcanar in the west of the city, the Puerta de Córdoba alcanzar in the north-east, and the Arriba alcanzar in the east. The latter was the main strength of the city since Islamic times. Under Pedro I, a number of changes were made to this Castle. Its defensive systems were strengthened in the context of the Castilian civil war, but the construction of an indoor palace was also initiated along the lines of those under construction in the rest of Castile under the promotion of the monarch. This article seeks to analyse what was the specific intervention of King Pedro I on Carmonan alcázar.