His pontificate was marked by the Arian controversy. He represented originally the position of Athanasius against Arianism. After he did not give up despite the threat this position which arianerfreundliche Constantius II, sole emperor banished him since 353, in the year 355 to Thrace and made Felix II Antipope. While in exile, however, Liberius then made concessions and sentenced last even Athanasius, to which he could return to Rome 358.
Liberius is the first non- canonized legitimate pope.
His observances are:
- Catholic: September 23
- Orthodox: August 27