At the death of his father in 741, an attempt was made to divide power between Carloman and his brother Pippin III and Grifo. Carloman and Pippin soon ousted Grifo, and each turned his attention towards his own area of influence, Pippin in the West and Carloman in the East.
Carloman strengthened his authority in part via his support of Boniface, the so-called "Apostle to the Germans." This was in part a continuation of a policy begun under his grandfather Pippin of Herstal and continued to a lesser extent under Charles Martel. Carloman donated the lands for Boniface's most important foundation, the monastery of Fulda.
He also was instrumental in the calling of the Concilium Germanicum, the first major Church synod to be held in the eastern parts of the Frankish kingdoms.
These actions strengthened Carloman's position, and that of the family as a whole, especially in terms of their rivalries with other leading families like the Bavarian Agilolfings. They also demonstrated a clear tendency in Carloman for pious actions.
In 747, Carloman renounced his position and withdrew to a monastic life. He died in 754.