[4] Little is known of Agatho before his papacy but he may have been among the many Sicilian clergy in Rome at that time, due to the Caliphate's attacks on Sicily in the mid-7th century.

[6] Shortly after Agatho became pope, Bishop Wilfrid of York arrived in Rome to invoke the authority of the Holy See on his behalf.

[7] The major event of his pontificate was the Sixth Ecumenical Council (680–681), following the end of the Muslim Siege of Constantinople,[8] which suppressed Monothelitism, which had been tolerated by previous popes (Honorius I among them).

Then a letter of Pope Agatho was read that explained the traditional belief of the Church that Christ was of two wills, divine and human.

[7] Agatho also undertook negotiations between the Holy See and Constantine IV concerning the interference of the Byzantine court in papal elections.

Constantine promised Agatho to abolish or reduce the tax that the popes had to pay to the imperial treasury on their consecration.