Wynnebald accompanied his elder brother Willibald to Rome around 720 and remained there as a student for seven years while Willibald continued to the Holy Land. He returned to Wessex briefly, then joined Boniface's German mission. After his brother became bishop of Eichstätt, Wynnebald founded around 752 the double monastery of Heidenheim on land granted by his brother — building much of it with his own hands.
He brought his sister Walburga from Wessex to govern the women's side of the foundation, becoming co-founder with her of one of the principal early Bavarian monasteries. Despite chronic ill health, he ran the men's community for nine years until his death in 761. Walburga survived him by nineteen years and is buried with him in the abbey church.