In 1088, he became the Archbishop of Vienna. He held strong views about the Investiture Crisis, but was willing to negotiate with Henry V, the Holy Roman Emperor.
In 1122 he concluded the Treaty of Metz with Henry V, by which the mutual rights of the church and the Empire were finally settled.
On September 23 of that year, the Concordat of Worms was agreed upon. The future emperor Honorius II was one of the papal negotiators.
In February 1119 he was chosen pope at Cluny in succession to Gelasius II., and in opposition to the anti-pope Gregory VIII., who was in Rome.
The journey of Calixtus to Rome early in 1120 was a triumphal march.
During his short reign Calixtus strengthened the authority of the papacy in southern Italy by military expeditions, and restored several buildings within the city of Rome.