Godfrey's parents were Count Eustace II of Boulogne and Ida, daughter of Duke Godfrey II of Lower Lorraine. Although he was named heir to the duchy of Lower Lorraine by his uncle in 1076, the Holy Roman emperor Henry IV kept the duchy for his son and left Godfrey with the lordship of Bouillon, in the Ardennes region of France. Godfrey won back his duchy in 1089 as a reward for his loyal service in Henry's war against the Saxons.

Godfrey, with his brothers Eustace and Baldwin, joined the First Crusade (Crusades) in 1096. When Raymond of Toulouse (Raymond IV) declined to become king of Jerusalem, Godfrey accepted the crown but refused the title of king and was called instead Advocatus Sancti Sepulchri (Defender of the Holy Sepulchre).

Godfrey arranged truces with the Muslim maritime cities of Ascalon, Caesarea, and Acre and successfully beat off an Egyptian attack. Godfrey also acknowledged himself as a vassal of Daimbert, patriarch of Jerusalem, thus laying the foundation for future struggles between lay and ecclesiastical figures who sought to control the kingdom. On his death he was succeeded by his brother Baldwin I.

Despite Godfrey's weakness as a ruler, the tall, handsome, and fair-haired descendant of Charlemagne was later idolized in legend and songs as the “perfect Christian knight, the peerless hero of the whole crusading epic.”