Despite residing in Sydney, Griffith was the candidate for the Labour Party for the seat of Waratah at the state election held on 12 July 1894. He was successful with 820 votes and was re-elected at elections in 1895, 1898 and 1901. In 1903 he resigned his seat to contest a Senate seat for New South Wales at the 1903 federal election. He was unsuccessful and as the by-election for Waratah was held prior to the Senate election, Griffith was denied the chance to recontest. In the following year, he was successful as the endorsed Labor candidate for the seat of Sturt at the general election of 6 August. Griffith was re-elected unopposed at the 1907 election but resigned from parliament the following year in protest at being suspended by the speaker when he protested the Speaker's alleged procedural unfairness. He won the subsequent by-election unopposed and continued to represent Sturt until the general election of 15 November 1913. A redistribution of state electorates resulted in Griffith stepping aside for John Cann the member for the abolished seat of Broken Hill. He successfully contested the Sydney electorate of Annandale, defeating the sitting member Albert Bruntnell.
Ministerial career
In the New South Wales Labor Governments of James McGowen and William Holman he was the Minister for Public Works, now NSW Public Works. From March 1915 until November 1916, he was the Minister for Public Education. As Minister for Public Works, Griffith encouraged the growth of state enterprises and increased spending on railway construction. Griffith had consistently advocated for the greater industrialization of Newcastle, then, Under Holman, he personally negotiated the establishment of a steelworks in Newcastle with G. D. Delprat of the Broken Hill Proprietary Co. Ltd., and was the architect of the Walsh Island establishment; though censured by the 1913 party conference cabinet for it, the scheme proved successful
Expulsion from Labor Party
During the ALP split over conscription in World War I he opposed the Labor Party's anti-conscription policy but did not follow Holman in joining the Nationalist Party. He subsequently resigned from the government and was expelled from the Labor Party. He contested the 24 March1917 election as an independent labor candidate but was defeated by William O'Brien the official ALP candidate. Griffith was one of the best known middle-class, professional supporters of the Labor party in its first 25 years. He maintained a socialist and republican stance throughout his public career.