Carloman has re-founded the palace and monastery at Ötting in Bavaria, dedicating it to the Virgin Mary and "numerous other saints whose relics we were able to collect with God's help", and appointing his father's friend, the linguistic scholar Baldo, as his chancellor.

He may have been the object in 878 of an assassination attempt.

According to the Annales Iuvavenses, the king "was surrounded by Count Ermenpert and some of his soldiers" at Ergolding, but the had count apparently fled to West Francia, where In a letter of June 7, 879, Pope John, having failed to persuade Louis the Stammerer, Charles the Bald's heir, to come to Italy for its defense, had appealed to Carloman, whom he had previously rejected.

It was too late.

Carloman had in 879 become incapacitated by illness, perhaps a stroke.

His brother Louis came to Bavaria to receive the recognition of the aristocracy as future king.

According to the Annales Fuldenses (879), Carloman lost his voice, but was still able to communicate by writing.

Regino of Prüm, writing for the year 880, recalls that he was "erudite in letters" (litteris eruditus), which indicates he could write Latin.

Most sources place Carloman's death in March 880, but the Annales Iuvavenses place it on September 21.Carloman leaves one illegitimate son, Arnulf, who continues as margrave of Carinthia during the reigns of Carloman's brothers.

In 887, he will become king of East Francia and in 896 emperor.