He was the brother of the Apostle Peter, from Bethsaida on the shore of Lake Gennesaret. Andrew left his fisherman's trade to become a disciple of St John the Baptist. Soon after the Forerunner had baptized Jesus, he said to Andrew and his other disciple John the Theologian, "Behold the Lamb of God!" At this, both disciples followed after Jesus. After conversing with Christ, Andrew hurried home and told his brother Simon Peter, "We have found the Messiah." For being the first to recognize Jesus as the Christ, St Andrew is called the First-Called.

After Pentecost, Andrew was appointed to preach the Gospel around the Black Sea and in Thrace and Macedonia, traveling as far as Lazica in the Caucasus. According to Slavic tradition his travels took him even further, into the land that was later to be called Russia.

In later travels the Apostle preached throughout Asia Minor with St John the Theologian, then traveled to Mesopotamia, then back to Sinope on the Black Sea, and finally to Patras in the Peloponnese, where he soon established a large community of Christians. One of his converts was Maximilla, the wife of Aegeates, the Proconsul of that region. Aegeates was so angered by his wife's conversion that he had the Apostle arrested and crucified head downwards on a cross in the shape of an "X." The holy Apostle rejoiced to be allowed to suffer the same death as his Master.

The holy relics of St Andrew, after various travels, were returned to Patras in 1964, where they are now venerated.

In the West, St Andrew is venerated as the patron of Scotland: in the Middle Ages, more than eight hundred churches in Scotland were dedicated to him.