Apart from the mentions of him in four of the Apostle lists (Mark 3:18, Matt. 10:3, Luke 6:14, and Acts 1:13), nothing is known about him from the New Testament. Bartholomew is a family name meaning “son of 【Hebrew: bar】 Tolmai, or Talmai,” so he may have had another personal name. For that reason and because he was always associated with the Apostle St. Philip in the Gospel lists, a 9th-century tradition identified him with Nathanael, who, according to John 1:43–51, was called with Philip by Jesus. Upon seeing Nathanael, Jesus said, “Behold, an Israelite indeed, in whom is no guile!” This identification sought to explain how the otherwise unknown Bartholomew could be mentioned in the Apostle lists, while Nathanael, whose call is explicitly described by John, does not figure in them. His full name would then be Nathanael bar Tolmai.

The 4th-century Bishop Eusebius of Caesarea in his Ecclesiastical History relates that, when the 2nd-century teacher St. Pantaenus of Alexandria made a visit to India, he found the Hebrew “Gospel According to Matthew,” which had been left behind there by Bartholomew. Traditionally, Bartholomew also served as a missionary to Ethiopia, Mesopotamia, Parthia (in modern Iran), Lycaonia (in modern Turkey), and Armenia. The apostle is said to have been martyred by flaying and beheading at the command of the Armenian king Astyages. His relics were supposedly taken to the Church of St. Bartholomew-in-the-Tiber, Rome.