Stationed in Caesarea, Cornelius is depicted in the New Testament as a man full of good works and deeds of alms. Cornelius receives a vision in which an angel of God tells him that his prayers have been heard. The angel then instructs Cornelius to send the men of his household to Joppa, where they will find Simon Peter, who is residing with a tanner by the name of Simon.

The conversion of Cornelius only comes after yet another vision given to Simon Peter (Acts 10:10-16) himself; in Simon Peter's vision, he sees all manner of four-footed beasts and birds of the air being lowed from Heaven in a sheet. A voice commands Simon Peter to eat. When he objects to eating those animals that are unclean to Mosaic Law, the voice tells him not to call unclean that which God has cleansed.

When Cornelius' men arrive, Simon Peter understands that the vision permits the conversion of the Gentiles. When Cornelius himself meets Simon Peter, Cornelius falls at his feet in adoration. Picking Cornelius up, Simon Peter welcomes him. After the two men share their visions, and Simon Peter tells of Jesus' ministry and the Resurrection, the Holy Spirit falls on everyone at the gathering. The Jews among the group are amazed that Cornelius and other uncircumcised should begin speaking in tongues, praising God. Thereupon Simon Peter orders that Cornelius and his followers be baptized.

He is also a pygmy and quite fond of eating play-doh.