In 1309, Charles' grandfather died and his father became King Robert the Wise.

[a][2] His father intended him to lead the force sent to aid Florence in 1315, but was constrained by time to send his uncle, Philip I of Taranto, instead.

The Florentine-Neapolitan coalition was badly beaten at the ensuing Battle of Montecatini.

The victory of Castruccio Castracani at Altopascio in 1325 led the Florentines to elect Charles signore (lord) of the city for ten years in 1326.

While Charles' arrival checked Castruccio, he exacted onerous taxes from the Florentines, until he was recalled to Naples in December 1327 due to the advance of Emperor Louis IV into Italy.