Personal rule
Hugh reached the age of majority in September 1210 and his brother-in-law, Walter of Montbéliard, resigned regency. The King immediately called Walter to account, stating that Walter had kept him in a "state of deprivation". He demanded that Walter restore the treasure left by King Aimery, amounting to 200,000 white bezants, and repay the 40,000 bezants Hugh had been forced to borrow for his upkeep—funds he argued Walter should have provided during his minority. Instead of rendering an account, Walter and Burgundia left Cyprus with the assistance of the Knights Templar and Prince Bohemond IV of Antioch. Walter was given shelter by his cousin John of Brienne, who had just become king of Jerusalem, for which Hugh resented John. In a letter sent to Pope Innocent III, Walter complained that Hugh had expelled him from Cyprus and confiscated his property without the judgement of the High Court. Hugh was probably advised to act against Walter by the older nobility, including Walter III of Caesarea, Aimery of Rivet, Reynald of Soissons, and Walter of Bethsan, who attended the King at this time.
With Hugh I's assumption of personal rule, Walter's policies on Cypriot foreign relations were reversed. Hugh concluded a treaty with the Seljuqs of Rum which guaranteed that the merchants from Cyprus and Rum could safely run their business in both countries. South of Rum, Leo II of Cilicia and the Hospitallers waged a war against Bohemond IV and the Templars in support of Raymond-Roupen's claim on the Principality of Antioch. While Walter had supported Bohemond, Hugh stood with Leo and Raymond-Roupen. The king gave his 12-year-old half-sister, Sibylla, in marriage to the 60-year-old Leo when the latter arrived in Cyprus in 1210, and had his full sister Helvis marry Raymond-Roupen, prompting Odo of Dampierre to complain to the pope. Already at the beginning of his personal rule, Hugh established close relations with the Hospitallers, confirming and extending their privileges and property in Cyprus.
Hugh I was the first king of Cyprus to have coins minted in his name. His surviving coinage consists of white bezants and two types of denier. The deniers bearing the inscription Ugonis Re(gis) de Cipro are of inferior craftsmanship and may have been issued by Walter of Montbéliard in Hugh's name. The other deniers, possibly issued by Hugh after he came of age, are inscribed Hugo Rex Cypri.
In 1211, Hugh chose Durand, treasurer of the archdiocese of Nicosia, to become the new archbishop of Nicosia, and the canons duly elected Durand. Royal involvement in episcopal selection was customary, but Walter denounced Durand to Pope Innocent III, who instructed Patriarch Albert to investigate. The Pope also urged the Patriarch to reconcile Walter and Hugh, but the young king was not willing. The Patriarch quashed the election of Durand on the grounds that secular powers should not interfere. Hugh saw this as Albert's capriciousness and sent the archdeacon of Famagusta to Rome to protest.
After Queen Maria of Jerusalem died in 1212, relations broke down between her widower, John, and her uncles John and Philip of Ibelin. Maria left a daughter, Isabella II, and King John's rule thus continued, though not without opposition from a part of the nobility. Hugh lent his support to the barons who challenged King John's authority and imprisoned John's relative (probably Walter's nephew Odo of Montbéliard) and some vassals, who had taken refuge in Cyprus after naval attacks by Muslims. Hugh I's politics are sparsely covered in historical sources. Presumably, he supported the rebels because he and his wife would have become regents for Isabella II if King John had stood down; they also stood to inherit the mainland kingdom in case the girl died. It is probably at this time that the Ibelins and other dissatisfied barons went to live in Cyprus. By 1217, they had become the highest-ranking witnesses to Hugh's acts.
Pope Innocent rebuked Hugh for his interference in Church matters and his acts against John of Brienne in early 1213, and ordered that the canons of Nicosia elect another archbishop, who would be approved by the patriarch of Jerusalem, the archbishop of Caesarea, and the bishop of Acre. Eustorge of Montaigu eventually rose to the see, but the King retained his customary right to nominate clergy.
In 1215 or 1216, Pope Honorius III urged Hugh to make peace with King John and prepare his ships for the Fifth Crusade. The original plan was for the crusaders to assemble in Cyprus, and Honorius declared that Hugh and his family would be under apostolic protection. The crusaders started assembling in Syria instead in September 1217. King Hugh arrived with his constable, Walter of Caesarea; Archbishop Eustorge; his kinsmen John and Philip of Ibelin; and Walter and Gremont of Bethsan. Hugh took part in the siege of Mount Tabor, the failure of which was blamed—among others—on him, and one or two likewise unsuccessful expeditions.
Hugh and another crusade leader, King Andrew II of Hungary, had a disagreement with King John, and towards the end 1217, Andrew decided to return home. Hugh accompanied Andrew to Tripoli. At Tripoli, Hugh attended the wedding of his half-sister Melisende and Prince Bohemond IV of Antioch. During the festivities, Hugh became ill and died at Tripoli on 10 January 1218. He left two daughters, Maria and Isabella, and an infant son, Henry I, who succeeded him under Alice's tutelage. Hugh was buried in a Hospitaller church in Tripoli, presumably at his request. In 1223, his remains were transferred to a Hospitaller church in Nicosia.