She was the seventh child of  Manuel Pedro Marto and Olimpia de Jesus dos Santos. She was born in the village of Aljustrel, parish of Fatima, in Portugal, on March 11, 1910.

After the visit from Our Lady, she separated herself from the things of earth in order
to turn her attention to heavenly things, and voluntarily consecrated her life so as to enter heaven one day. She was constantly contemplating  God. She sought silence and solitude.

She said: "I love Our Lord so much! At times, I seem to have a fire in my heart, but it does not burn me." She dearly loved  Our Lord and would often cry on hearing the Passion. She then declared that she would never wish to commit a sin in order not to make Jesus suffer. She visited frequently and for long periods in the parish church, concealing herself in the pulpit where no one could see or distract her. She longed to receive Communion, but she was too young .  She prayed the Rosary daily. She offered prayers and sacrifices for the Pope, for the salvation of souls and for the conversion of sinners.   In fact, not a few of her sufferings were caused by those who doubted or did not believe the apparitions to be true; she was called a liar and a fraud; imprisoned for some days. She bore all of this in silence and was happy to do it.  She restrained her will and her temperament, and was obedient to her parents and to her older brothers and sisters; she did without food to give it to the poor; she did not drink water, especially in the summer heat; as a form of penance she wore a rope around her waist; (remember Our Lady told her wear it only in the daytime). She always remembered the words of Our Lady and  prayed: "O my Jesus, it is for love of You, for the conversion of sinners, and in reparation for the sins committed against the Immaculate Heart of Mary."

In October 1918, one year after the last apparition, Jacinta developed pneumonia and then pleurisy. She was taken to a hospital at Ourem. After two months she returned home with an incision in her chest. A doctor on pilgrimage visited Jacinta and said she should go to the children's hospital in Lisbon. So Jacinta and her mother started their journey.

When Jacinta was at the hospital in Lisbon the doctors talked about performing an operation. She said that it would all be in vain because she was going to die. She even had someone write to Lucia informing her of the day and hour of her death.

Because of her weakened state, only a local anesthesia could be given for the operation.  They removed two ribs and left an open wound in her chest. She suffered very much but never complained.

On February 20th, 1920, she died.  She was where she had longed to be, with Our Lord and His Blessed Mother.  She was buried in the vila Nova de Ourem.
Fifteen years later her body was moved to a cemetery at Fatima and was found incorrupt.

Lastly, she was moved to the sanctuary built on the spot where the Our Lady appeared to her