Nobly born in France, in 1096 he accompanied his uncle Bohemund of Taranto on the First Crusade, his participation being notable in several respects. In Constantinople he refused to swear an oath to the Byzantine emperor Alexius I promising to return all conquered lands to the Byzantine Empire; many European nobles did swear, and would later renege.
He participated in several sieges during the First Crusade, including the conquests of Nicaea, Tarsus and Antioch. During the assault on Jerusalem in 1099, Tancred was one of the first crusaders to enter the city; for the rest of his life he would claim, along with number of others, to have been the first.
After the establishment of the Kingdom of Jerusalem, Tancred became Prince of Galilee and expanded his power base through the misfortunes of others. In 1100 he assumed control of the Principality of Antioch while his uncle as a prisoner; later, when Baldwin II was made captive by Muslims in 1104 he assumed control of the County of Edessa as well. After Baldwin was released they fought over control of Edessa and Tancred was defeated, retiring to Antioch.
As Prince of Galilee Tancred often fought the Christian Byzantines as much as the Muslim Saracens, for his remaining years he frequently warred against Alexius I and refused to acknowledge the Treaty of Devol, an agreement between Bohemund and Alexius.
Tancred died in Antioch, of typhoid, in 1112 CE. Although married, he left no heirs.