Treworgie was granted the governorship of Newfoundland in 1653; he was already in Ferryland, apparently never having left after 1651. The next year, he and two other commissioners were arrested by James Kirke for holding possession of lands rightfully owned by the Kirkes, and an unpaid debt of £1,100. Treworgie maintained that Kirke's possessions had been returned to his wife, but was found guilty in a first trial. A personal plea to Cromwell resulted in a second trial. The outcome is lost, but it appears that Treworgie was found not guilty, as he continued to serve as governor until 1660. In 1660, Treworgie returned to England to ask for another term as governor and for six year's salary he claimed he was owed. He never returned to Newfoundland.