He was the eldest son of King Vratislaus II and Adelaide, daughter of Andrew I of Hungary.

Bretislaus also wished to end the elective principle of succession and replace it with a type of seniorate as conceptualised by Bretislaus I: the eldest prince of the reigning family would hold Bohemia as sovereign over the entire state while the younger scions of the dynasty would rule as territorial dukes over the regions of Moravia.

He invested Bořivoj as duke of Brno in 1097, thus removing the sons of Conrad I from the succession.

Bretislaus also succeeded in receiving a long-desired imperial investiture at the Diet of Regensburg on 19 April 1099.

Bretislaus was assassinated by his adversaries at the hunting lodge of Zbecno in western Bohemia on 22 December 1100.