In the Museum of Sacred Art there are some very valuable pieces that are part of the treasure of the Monastery of Santa Cruz. Highlights include the Chasuble that belonged to the Martyrs of Morocco, in fabric of Moorish origin, dating from the 13th century, and also some vestments, from the 18th century, embroidered with gold thread, as well as some liturgical implements.​

In the so-called Treasury Chapel, the Silver Reliquary Bust (dated 1610) stands out, containing the skull of Saint Teotónio (visible through the crystal in the “chest”), one of the founders of the Monastery and its first prior and first Portuguese Saint. (He was canonized in 1163, one year after his death).

This reliquary is flanked by two smaller reliquary busts, also in silver (dated 1510) with the relics of the Martyrs of Morocco.