Géza died in 1077, and his supporters made Ladislaus king. Solomon resisted Ladislaus with assistance from King Henry IV of Germany. Ladislaus supported Henry IV's opponents during the Investiture Controversy. In 1081, Solomon abdicated and acknowledged Ladislaus's reign, but he conspired to regain the royal crown and Ladislaus imprisoned him. Ladislaus canonized the first Hungarian saints (including his distant relatives, King Stephen I and Duke Emeric) in 1085. He set Solomon free during the canonization ceremony.

After a series of civil wars, Ladislaus's main focus was the restoration of public safety. He introduced severe legislation, punishing those who violated property rights with death or mutilation. He occupied almost all Croatia in 1091, which marked the beginning of an expansion period for the medieval Kingdom of Hungary. Ladislaus's victories over the Pechenegs and Cumans ensured the security of his kingdom's eastern borders for about 150 years. His relationship with the Holy See deteriorated during the last years of his reign, as the popes claimed that Croatia was their fief, but Ladislaus denied their claims.