After the crusaders captured Jerusalem in 1099, Warner was one of the few who remained there with Godfrey. When Godfrey fell sick in 1100, Warner and Tancred, Prince of Galilee prepared a siege of Haifa with the Venetian fleet that had anchored at Jaffa. Warner became ill during the preparations and did not accompany the siege, but as Albert says, he was "conveyed to Jerusalem on a litter."