Evans entered parliament as the Country Party member for Lachlan after he won the seat at 1938 state election. The long-term incumbent Country Party member and former party leader Ernest Buttenshaw had retired and Evans successfully contested the election against two other endorsed Country party candidates. He was 69 years old at the time of his initial election. In parliament he opposed several moves to place age limits on public servant positions and was noted for occasionally voting against his party's position.[3] Evans retained the seat at the 1941 state election,[4] but died suddenly in office two years later. He did not hold party, parliamentary or ministerial office.[2]
In 1949, the Northern Riverina Football League, best and fairest player was awarded the Griffith P. Evans Cup, named after local solicitor and a former NSW State Member for Lachlan, whose family donated the cup.[5] The best and fairest player in the NRFL is now awarded the Evans Medal.