Andrew Duncan was a writer in Lerwick and a Lerwick Town Councillor between 1829 and 1832. He was the eldest son of Andrew Duncan, Sheriff Substitute for Shetland, and a nephew of fellow councillor Gilbert Duncan. He was elected to the council on 3 September 1829, styled "Andrew Duncan Junior, Writer" in the minute book to distinguish him from his father, who presided over the same meeting as Sheriff. He served until the election of 6 September 1832, at which he was not returned. As a lawyer he represented the plaintiff in Eunson v. Bruce of Symbister, a tenancy dispute that ran through the late 1840s and early 1850s.