In 1165, the previous Bishop of Toul, Henry I of Lorraine, died; two years later, Peter was elected to succeed him, and consecrated by Hillin of Falmagne, Archbishop of Trier, of whom he was a suffragan.
Thereafter, he put an end to the war between Frederick IV of Dampierre, Count of Toul, and the cathedral canons, and by 1177 had rebuilt the castle of Liverdun, destroyed in the strife, making it and the associated town a nexus of power in the diocese.
In the succeeding years, he himself came into conflict with the powerful Matthias I, Duke of Lorraine, who sought to gain the rents of the church of Toul for his son, Theoderic, Bishop of Metz; Peter appealed the case to Alexander III, but the Pope was unable to intervene due to his ongoing struggle with Barbarossa.
Peter was a strong supporter of the interests of Barbarossa, both paying numerous lengthy visits to the imperial court and himself playing host in Toul to the Emperor twice, in 1171 and at Pentecost of 1187.
After the Treaty of Jaffa between Saladin and Richard the Lion-Heart was signed on September 2, 1192, allowing Christians free access to Jerusalem, he made his way there, where he died and was buried.