The cathedral was erected on command of King Sancho Ramírez, who, after renovating in Rome his vassal oath[clarification needed] to the Pope Alexander II (1068), had obtained from the latter the right to establish the episcopal seat in Jaca, then capital of the Kingdom of Aragon.

In Baroque times the St. Horosia Chapel, the loggia and the cloister were added, while the interior received an altarpiece and other decorations.

The plan is in the forms of a nave and two aisles, with three apses and two external portals, both provided with loggias (one of which in Renaissance style).

The nave and the aisles are separated by arcades supported by piers which are alternatively cruciform and cylindrical in plan, an element inspired by contemporary French structures.

The earlier ones (those dedicated to the Holy Cross and to St. Augustine) are late Gothic in style, those designed in the 16th century (St. Michael and St. Jerome, for example) show late Renaissance and Mannerist influences; the chapel of St. Horosia, completely remade in the 18th century, is in Baroque style.