This magnificent monument comprises three naves, with embedded chapels and slender vaults. The interior produces an effect of great height, due to the absence of capitals on the piers. The chancel, created in the Flamboyant Gothic style, has plain pinnacles and butresses of great simplicity. Its ornamentation was either removed or uncompleted.

The west façade and its two towers were finished at the beginning of the 18 C. On this façade can be seen a variety of sculptural styles, with all types of decorative elements. The splayed door is crowned by a shell with three compartments where different events from the Gospels are illustrated, and on both sides two large reliefs represent the Pardoning of the Adulterous Woman and the Expulsion of the Moneylenders from the Temple.

In the interior of the temple is the beautiful retable of the High Altar, one of the masterspieces of the 16C Spanish art. It has been restored recently to house the exhibition "The Ages of Man. Crossroads" in the year 2000. Among its many representations are the "virtues" and events in the lifes of Jesus and the Virgin, sorrounded by a multitude of big angels whose bodies are surprisingly human.

The Cathedral includes other excellent retables, such as the Flemish-Spanish San Miguel retable that includes some delicate panels representing events in the life of Jesus. On its low part there are half-length figures. The Majestad retable was named after the Virgin of Majestad, who is represented by a carving housed in its niche. The retable contains interesting paintings by Juan de Peñalosa, representing saints before and after the Trento Council as well as a religious scene of great historical value because it reflects the atmosphere in Astorga at that time. San Jerónimo´s retable displays several panels illustrating events in the life of the saint. They have an excellent composition and are very expressive.