One of the most important clues to the approximate time of his accession is the contemporary Frankish chronicle Annales Fuldenses, which mentions several West Slavic princes in the year 872, among them one Goriwei, who may be identical with Bořivoj.

According to the early 12th-century Chronica Boëmorum, Bořivoj was a son of the legendary Bohemian prince Hostivít, thus a descendant of Queen Libuše and her husband Přemysl the Ploughman.

As the head of the Přemyslids who dominated the Central Bohemian environs, Bořivoj declared himself kníže ("prince")—in Latin dux, which means a sovereign prince—around the year 867 AD.

[citation needed] Bořivoj was recognised as such around 872 by his overlord King Svatopluk I of Moravia, who dispatched Bishop Methodius of Thessalonica to begin the Christianization of Bohemia.

When Bořivoj died about 889, his sons still minors, King Svatopluk concluded an agreement with the East Frankish ruler Arnulf of Carinthia and took over the rule of the Bohemian duchy himself.