Baudouin was born about 940, the son of Arnulf I, count of Flanders, and Adela de Vermandois. Arnulf I had made Baudouin co-ruler in 958.
In 961 Baudouin married Mathilde of Saxony, daughter of Hermann Billung, duke of Saxony. Baudouin and Mathilde had a son Arnulf II, who would have progeny.
During his short rule, Baudouin established the weaving industry in Ghent, laying the basis for the economic importance of the county in the centuries to come.
Baudouin died before his father on 1 November 962, and was succeeded by his infant son Arnulf II, with his father acting as regent until his own death in 965.