He ruled from his seat in the fortified town of Bribir, where he erected, along with his castle, the three-aisled basilica of St. Mary inside the Franciscan convent.

[4] After the extinction of the Árpád dynasty, Paul had the Angevins brought to the throne, although their power over the land held by the Šubić family was merely nominal throughout the entirety of their administration.

Paul took extensive campaigns and significantly expanded his dominion eastward, over Bosnia and Hum, and also warred successfully against the Republic of Venice, taking the Dalmatian capital Zadar.

His wife Helen, was a relative of the Capetian House of Anjou, and Mladen already made marriage contracts of their children to the counts of Gorizia, which could serve as valuable allies in the war against the Republic of Venice.

In 1317, Matej Zori was eventually ousted from his position and was driven into exile by certain outer elements, with the help of the city of Šibenik, an act which was supported by Mladen.

He inherited a dispute from his father regarding Jablanac, with the noble Frederick III (Frankopan) of Krk, although this did not pose any significant threat.

A larger threat emerged from a rebellion of counts Nelipić and Kurjaković in the winter of 1316–1317, probably in connection with his conflicts against the Slavonian Babonić nobles.

In the aftermath, his younger brother George II (who was the prince of Omiš) was given as a hostage to the opposing side as part of the peace negotiations, and was subsequently transferred to the city of Dubrovnik for safe keeping.

This act only deepened the conflict and provoked other members of the Croatian nobility to mutiny, including his younger brother Paul II, who was at the time Duke of Trogir.

[6] The rebellion of the cities received support from Venice and in March 1322, Šibenik accepted Venetian rule, who in turn sent a fleet to defend it from Mladen's attempts at retribution.

[6] This forced Mladen to convene an assembly of the Croatian nobility in order to gain support and tone down the tensions with the Dalmatian cities.

Mladen's army consisted of his own troops, those of his brother George II, as well as Vlachs' and those from lesser nobility of the Poljica region.

The opposing army were royal troops under John Babonić in coalition with the Croatian nobility (including Paul II Šubić) and the militia of Trogir and Šibenik.

[6] In the Klis Fortress, Mladen received news of the king's arrival in Knin, which prompted him to send his younger brother George II as a diplomat with intent to negotiate.

Historians give various reasons for Mladen's failure in relation to the career of his father, namely his violent tendencies and vanity, although those were not unusual traits for a ruler.

His power as an arbiter became a burden for the Dalmatian cities, whose aristocracy and citizens required more space for self-governing, which was impossible to do with the domination of Mladen's court members.

In the document of 10 April 1318, Mladen II Šubić is called "Ban of the Croats and Bosnia and general lord of Hum country".