In the year of Coloman's coronation, at least five large groups of crusaders arrived in Hungary on their way to the Holy Land. He annihilated the bands who were entering his kingdom unauthorized or pillaging the countryside, but the main crusader army crossed Hungary without incident. He invaded Croatia in 1097, defeating its last native king Petar Svačić. Consequently, he was crowned king of Croatia in 1102. For centuries thereafter, the Hungarian monarchs were also the kings of Croatia.

Coloman had to face his brother's attempts to dethrone him throughout his life; Álmos devised plots to overthrow him on at least five occasions. In retaliation, he seized his brother's duchy in 1107 or 1108 and had Álmos and Álmos' son Béla blinded in about 1114.