In 1540, the parish priest of Berriz, Martín de Aguirresacona, made a will in favour of the community of lay sisters of Berriz, founding a convent with the name of the Vera Cruz.
The convent adopted enclosure in 1550 after three women, one of them the sister of the founder, took the habit of the Blessed Virgin Mary of Mercy.
The convent’s life was austere. Nuns worked inside and outside the house to sustain the community. They also gathered alms for the redemption of captives, the goal of their order.