Born in Liverpool in 1854, George Mahon's family moved to Ireland when he was a child, where he was educated. He returned to Liverpool and became a senior partner in Roose, Mahon & Howard, a leading firm of accountants who were based in North John Street.

He was the organist at St Domingo's church between 1891-92 and along with the Revd. B.S. Chambers formed a football team in order for the church's cricket team to have something to do during the winter months. That football team started life as St. Domingo's in 1878 and became Everton a year later.

In January 1892 George Mahon became a major influence in the decision to leave Everton's then home, Anfield, following a huge rent rise for the ground by the landlord, John Houlding. He announced at a committee meeting that he had an option on a field at Mere Green which stood on Goodison Road and with considerable help from fellow committee member, Dr. James Baxter, acquired the plot of land that was to become Goodison Park. In May 1892 Mahon was elected to Chairman of the club, a position he held until 1895 when he resigned along with several fellow Directors due to 'acute administrative differences' but was persuaded to remain on the board by the shareholders.