The
altarpiece over the main altar is
The Crucifixion (1564-1565), by
Girolamo Siciolante da Sermoneta. Funded by
Prince Philip of Spain it was moved from
San Giacomo degli Spagnoli. The three chapels on the right side were built between 1582 and 1588; those on the left between 1592 and 1594. The vault of the nave was erected between 1596 and 1598. That of the apse, between 1673 and 1675, under the direction of the Roman architect Giovanni Battista Contini. In the niches above the lateral doors are statues of two Aragonese saints (1816),
St. Isabel of Portugal and
St. Peter Arbués, by the sculptor Juan Adán. The entire interior was renovated by Giuseppe Camporese between 1818 and 1821, when the high altar was also built. The high altar was consecrated in 1954.
Chapel of San Diego de Alcalá The first chapel on the right, dedicated to
San Diego de Alcalá, contains a burial plaque of Cardinal
Bernardino Rocci (died 1599) on the pavement with his heraldic shield on the ceiling. The altarpiece depicting
San Diego di Alcantara was painted by
Annibale Carracci. The framing conch were added in the 19th century. The sepulchral monuments of Félix Aguirre (died 1832), José Álvarez Bouguel (1805-1830), and of the ambassador of Spain Antonio Vargas Laguna (died 1824) were completed by
Antonio Solá. On the left is the tomb of Bishop Alfonso de Paradinas and on right, the tomb of the bishop of Terni, and secretary to Pope Alexander VI,
Juan de Fuensalida (died 1498), both attributed to the work of
Andrea Bregno. File:Roma, chiesa di Santa Maria in Monserrato degli Spagnoli - Abside e organo a canne.jpg|Main altar File:Regola - s M Monserrato cappella sx2 1050571.JPG|Chapel of Our Lady of Monserrat File:Santa Maria in Monserrato Alfonso de Paradinas 1.JPG|Funeral monument of Bishop Paradinas File:Santa Maria in Monserrato degli Spagnoli Ceiling.jpg|Ceiling File:Door Santa Maria in Monserrato degli Spagnoli.jpg|Entrance == Burials ==