He was the eldest son of Rudolf of Rheinfelden, duke of Swabia, and German anti-king (r.1077–1079) in opposition to Henry IV of Germany.
Henry, however, appointed Frederick of Stauf, who had lands strategically located much to his advantage.
He eventually left the fight to his brother-in-law, Berthold II, Duke of Swabia, and Welf IV.
When Berthold died without descendants in 1090 and was buried in the monastery of Saint Blaise.
Berthold II, who was married to his sister, Agnes of Rheinfelden succeeded him as duke of Swabia.