He ruled over an area which included Prizren, Skopje and Prilep, and had good relations with his brother, Despot Jovan Uglješa who ruled an area around Ser. Later he became strong enough to disobey Uroš.
In 1371, he established a coalition with his brother against the Ottomans. The Serbian-Bulgarian army of the coalition numbering ca. 70,000 men met the Ottoman army led by beylerbey of Rumeli Lala Şâhin Paşa at Battle of Maritsa on September 26, 1371 where superior Ottoman tactics won over outnumbering coalition army. Vukašin's forces are routed and himself killed during the battle.
Brian Aldiss - published an alternative-history fantasy story "The Day Of The Doomed King" about King Vukašin