De León was born on March 23, 1643, in the town of El Sauzal, located on the island of Tenerife, one of the Spanish Canary Islands, to Andrés de León y Bello and María Delgado y Perera, a humble family of noble origin, although in decline.
She was of possible Guanche ancestry.

She was their youngest child, having two sisters and a brother.
According to the chronicles of the time, she was a woman of delicate features and a sweet face.

From an early age, De León showed mystical inclinations, especially in her feelings and great devotion to a miraculous image of the baby Jesus that was in the Church of St. Peter in her hometown.
This image supposedly would open the doors of the church for her when she went to pray before it.
There was also a laurel tree which would grow only under her care.

With the death of De León's father in 1646, poverty overtook the family.
Around this time, a couple from mainland Spain, who had relocated to the city of San Cristóbal de La Laguna, where the husband was to practice medicine, had decided that they wanted another child to care for, along with their own child.
Her mother, María Delgado, was convinced to give up her daughter by the doctor's wife with the promise of a better life for the child.
Two years later, the couple made plans to move to New Spain, with the intention of taking Mary with them.
Before this could happen, she was recovered by her birth mother, who had learned of this plan.
Delgado, however, died shortly after this, and her daughter was taken in by a good friend of her mother who lived in La Orotava.

When De León was reaching her teenage years, two local women, who had the reputation of leading simple lives, came to her foster mother, with a letter supposedly from the girl's maternal aunt, Catalina Delgado, which said that she and her husband wished to care for the girl, and the bearers should accompany her to their farm.
They then took her back to the city of San Cristóbal de La Laguna, where one of them approached a man in a back alley of the city.
De León quickly realized that she was in danger and made her escape.
She went to her aunt's home, where she was received and cared for by her and her uncle.

Living there, De León gradually took over the care of the farm, doing the hardest jobs and organizing its operations.
She would rise at dawn and spend the entire day at work, never showing signs of fatigue.
Her spiritual qualities soon became apparent, as she treasured solitude and embraced the lowliest work.
She led a life of strict penance, wearing the simplest clothing and sleeping on the floor.
Over time, the farm flourished and her uncle, Miguel Pérez, felt that she should be the one to inherit their land.
He drew up a will for this on 23 March 1665.
Mary was torn.
She felt a desire to live a religious form of life, one in which she could do the most needed work, living in total poverty, without even the dowry her inheritance would have provided.
Finally she declared her intention to enter a monastery as a lay sister, a decision which her aunt and uncle accepted.

Initially De León's guardians wanted her to enter the local monastery of the Poor Clares as the servant of their daughter, a choir nun in that community.
She chose, however, to enter the monastery of the nuns of the Dominican Second Order, although she originally wanted to belong to the Order of Discalced Carmelites, as she was very devoted to their foundress, St. Teresa of Jesus.
As there had not yet been established any monasteries of the Discalced Carmelite nuns in the Canary Islands, De León entered the Dominican Order, due to a mysterious dream she had.
De León was born on March 23, 1643, in the town of El Sauzal, located on the island of Tenerife, one of the Spanish Canary Islands, to Andrés de León y Bello and María Delgado y Perera, a humble family of noble origin, although in decline. She was of possible Guanche ancestry.
She was their youngest child, having two sisters and a brother. According to the chronicles of the time, she was a woman of delicate features and a sweet face.
From an early age, De León showed mystical inclinations, especially in her feelings and great devotion to a miraculous image of the baby Jesus that was in the Church of St. Peter in her hometown. This image supposedly would open the doors of the church for her when she went to pray before it. There was also a laurel tree which would grow only under her care.
With the death of De León's father in 1646, poverty overtook the family. Around this time, a couple from mainland Spain, who had relocated to the city of San Cristóbal de La Laguna, where the husband was to practice medicine, had decided that they wanted another child to care for, along with their own child. Her mother, María Delgado, was convinced to give up her daughter by the doctor's wife with the promise of a better life for the child. Two years later, the couple made plans to move to New Spain, with the intention of taking Mary with them. Before this could happen, she was recovered by her birth mother, who had learned of this plan. Delgado, however, died shortly after this, and her daughter was taken in by a good friend of her mother who lived in La Orotava.
When De León was reaching her teenage years, two local women, who had the reputation of leading simple lives, came to her foster mother, with a letter supposedly from the girl's maternal aunt, Catalina Delgado, which said that she and her husband wished to care for the girl, and the bearers should accompany her to their farm. They then took her back to the city of San Cristóbal de La Laguna, where one of them approached a man in a back alley of the city. De León quickly realized that she was in danger and made her escape. She went to her aunt's home, where she was received and cared for by her and her uncle.
Living there, De León gradually took over the care of the farm, doing the hardest jobs and organizing its operations. She would rise at dawn and spend the entire day at work, never showing signs of fatigue. Her spiritual qualities soon became apparent, as she treasured solitude and embraced the lowliest work. She led a life of strict penance, wearing the simplest clothing and sleeping on the floor. Over time, the farm flourished and her uncle, Miguel Pérez, felt that she should be the one to inherit their land. He drew up a will for this on 23 March 1665. Mary was torn. She felt a desire to live a religious form of life, one in which she could do the most needed work, living in total poverty, without even the dowry her inheritance would have provided. Finally she declared her intention to enter a monastery as a lay sister, a decision which her aunt and uncle accepted.
Initially De León's guardians wanted her to enter the local monastery of the Poor Clares as the servant of their daughter, a choir nun in that community. She chose, however, to enter the monastery of the nuns of the Dominican Second Order, although she originally wanted to belong to the Order of Discalced Carmelites, as she was very devoted to their foundress, St. Teresa of Jesus. As there had not yet been established any monasteries of the Discalced Carmelite nuns in the Canary Islands, De León entered the Dominican Order, due to a mysterious dream she had.
Mary of Jesus de León y Delgado