In 1184, his father, Béla III of Hungary, ordered that he be crowned king, and appointed him as ruler of Croatia and Dalmatia around 1195.

During the first four years of his reign, he fought his rebellious brother, Andrew, who forced Emeric to make him ruler of Croatia and Dalmatia as appanage.

Emeric was the first Hungarian monarch to use the "Árpád stripes" as his personal coat of arms and to adopt the title of King of Serbia.

[8][9] Leopold VI, Duke of Austria, intervened on behalf of Andrew, and at the end of the year, their combined forces routed Emeric's troops at Mački, Slavonia.

[2][12] On 10 March 1199, Emeric forced Boleslaus, Bishop of Vác, who was a supporter of Andrew, to give him documents that proved the conspiracy against him.

[17][13] Upon Emeric's request, the Pope refused to send a royal crown to Grand Prince Stephen of Serbia.

[16][19] He was also the first king to use a royal seal depicting the so-called "Árpád stripes", which eventually became part of the coat of arms of Hungary.

[21][22] Even though Pope Innocent III forbade the crusaders to besiege Zadar, they seized the town on 24 November and gave it to the Venetians.

[20] Emeric walked into his brother's camp unarmed, stating, "Now I shall see who will dare to raise a hand to shed the blood of the royal lineage!

[20] Taking advantage of the civil war in Hungary, Kaloyan invaded and captured Belgrade, Barancs (now Braničevo in Serbia), and other fortresses.

He reconciled with his brother, "entrusting to him the guardianship of his son and the administration of the entire kingdom until the ward should reach the age of majority",[31] according to Thomas the Archdeacon.