Mather was educated at Paisley Grammar School and Greenock High School before attending the University of Glasgow. Before his election to Holyrood he worked as a chartered accountant and ran his own business. He joined the SNP in 1996 and acted as the SNP’s National Treasurer from 2000.
He was the SNP candidate in the 2000 Ayr by-election and was their candidate for Argyll and Bute at the 2003 where he came third. He was elected to the Scottish Parliament as a regional list member for the Highlands and Islands. In opposition he was the SNP's Shadow Enterprise and Economy Minister.
