András was born about 1015, a son of Vazul (Basil) 'the Blind' of Hungary, lord of Gran and regions roughly corresponding with today's Slovakia. His mother was said to be a daughter of the Tsar of Bulgaria. She has been identified as either Katun Comitopuli of Bulgaria or Katalin of Bulgaria. András was from a younger branch of the Arpád dynasty. Hungarian tribal society favoured patrilineal seniority, not primogeniture, to determine the order of succession, which made other males of the Arpád dynasty in cadet lines dangerous to the incumbent king. András' branch of the dynasty had long been rivals of the older branch, to which Stephan I of Hungary and his father belonged. For the preceding half century the rivalry had centred much on the conflict between paganism and Christianity, representing (and used), respectively, by the younger and older branches. The older branch went extinct in the male line with Stephan's death in 1038, which opened up new opportunities for the younger, surviving male line. Stephan's female-line successors Aba Samuel and Peter Orseolo felt it necessary to suppress the rival family.
A period of dynastic struggle following Stephan's death was concluded after the death of Stephan's brother-in-law Peter Orseolo, when András took the Hungarian throne for his branch of the Arpád dynasty.
Under the rule of Stephan's other brother-in-law Sámuel Aba, András and his brothers Levente and Béla had been exiled from Hungary, fearing for their lives. First fleeing to Bohemia, they continued to Poland where Béla married into that royal family. András and Levente, possibly feeling overshadowed by their brother, continued on, settling in Kiev, and András married Anastasia, a daughter of Jaroslav I Vladimirovitch, grand duke of Kiev.
Their return to Hungary in 1046 sparked the Vatha pagan rising, in which András through pagan support managed to wrest the crown from Peter Orseolo. András was crowned in 1047 and strengthened his rule by military success, in part thanks to pagan support. Nevertheless, he continued the policies of Christianisation that had previously been in place. As Hungarian king, András remained an ally of his former hosts in exile, the Kievan Rus'.
The relationship with the Holy Roman Empire remained tense. The previous king, Peter Orseolo, had been a close ally of Emperor Heinrich III, and during his second reign, after the interlude of the reign of Sámuel Aba, Hungary had been part of the Holy Roman Empire. Heinrich now undertook two largely unsuccessful campaigns against Hungary, in 1051 and again in 1052. András then formed an alliance in 1053 with Konrad II, duke of Bavaria, thereby supporting the opposition to the emperor.
In 1057 András tried to ensure his succession by having his five-year-old son Salomon crowned as king. This proved unsuccessful, as in 1060 András' brother Béla I managed to unseat András and gain the throne, if only for a short time.
András, who was wounded in the battle against Béla, sent Salomon to Germany for safekeeping, and died in 1061. He and his family are buried in the Tihany abbey, founded by him on the shores of Lake Balaton.
His son Salomon followed his uncle Béla I as king of Hungary from 1063 to 1071, but neither of Salomon's sons (Salomon and David) left surviving male descendants, and the younger line of Béla prevailed after Salomon's death, with first Béla's son Geisa then Geisa's brother Laszlo; Laszlo was followed by Geisa's son Kalman. András' daughter Adelheid married Wratislaw II, king of Bohemia; however the descent continued only through her daughter Judith, who married Wladyslaw I Herman, king of Poland and became the mother of Boleslaw III Krzywousty, king of Poland, the great-grandson of András. And so the line from András continued not in Hungary, but in the Piast dynasty of Poland.