Anicetus was pope from about 154 to about 167 (the Vatican's list cites 150 or 157 to 153 or 168). He was a Syrian from Emesa. According to Irenaeus, it was during his pontificate that the aged Polycarp, a disciple of Saint John the Divine, visited the Roman Church. Polycarp and Anicetus discussed the celebration Easter. Polycarp and his Church of Smyrna celebrated Easter on the fourteenth day of Nisan, which coincides with Pesach. The day of the week was not important in the East. On the other hand, the Roman Church celebrated Easter on Sunday—the weekday of Jesus' resurrection. The two did not agree on a common date, but Anicetus permitted Polycarp and the Smyrnan Church to retain the date to which they were accustomed. The controversy was to accelerate and grow heated in the course of the following centuries.

The Christian historian Hegesippus also visited Rome during Anicetus' pontificate. This visit is often cited as sign for the early importance of the Roman See.

Anicetus was the first pope to condemn heresy by forbidding Montanism. He also actively opposed the Gnostics and Marcionism. According to Liber Pontificalis, Anicetus decreed that priests are not allowed to have long hair (perhaps because the Gnostics wore long hair.) Anicetus is reported to have suffered martyrdom. April 16, 17 and 20 are all cited as the date of his death, but April 17 is celebrated as his memorial or feast day. Details relating to the type of his martyrdom are unknown.