Makin was born in Sydney to a working-class family and moved frequently during his youth, settling in South Australia in 1911.

Having been involved in the labour movement from an early age, Makin was president of the North Adelaide district branch of the Amalgamated Society of Engineers in 1914 and secretary of its political committee in 1917.

[11] Makin was a lifelong Methodist, and in 1977 received a certificate from the church commending him on having been a lay preacher for seventy years.

[17][18] Following the defeat of the Scullin government in 1931 amidst the split, Makin was an outspoken loyalist of official Labor, alleging that he had been subject to an attempt to bribe him to leave the party, condemning both the pro-Premiers' Plan and Lang Labor defectors, and repeatedly clashing with Premier Lionel Hill.

[29] By 1941, when Labor returned to power under John Curtin, of who Makin was a close supporter, Makin had an undeniable claim to office, and became Minister for the Navy and Minister for Munitions, responsible for the Department of Munitions which oversaw the Small Arms Ammunition Factories around the country.

[31] He established good relations with service chiefs and played an important role in Australia's successful transition to a wartime economy, and later advocated for munitions factories to be retained in government control and adapted to civilian use to boost post-war manufacturing.

[32] When Curtin died in 1945, Makin contested the leadership ballot along with Ben Chifley and caretaker Prime Minister Frank Forde.

[34][35] He was Acting Minister for External Affairs for four months during the absence overseas of Herbert Evatt until January 1946 while negotiations for the Australian–Thai Peace Treaty took place and Australia re-established a Commissioner in Singapore.

[36][37] In January 1946, he was selected by Chifley to lead the Australian delegation to the first General Assembly of the United Nations, having previously represented Australia at the London conference in early 1945.

The selection of Makin was nonetheless criticised by the opposition and some media due to a perception that he lacked experience in external affairs and did not have the stature of a figure such as Evatt.

[47] His presidency included responses to the Iran crisis of 1946, the Indonesian National Revolution and the presence of British troops in Greece, and the appointment of the first Secretary-General.

[51][52] The Sydney Morning Herald reported that Makin's chairmanship had been "scathingly criticised in the lobbies" in England, while The Daily Mirror defended Makin, stating that he had "conducted proceedings with scrupulous fairness, great care, obvious sincerity and no small degree of skill", and deriding what they labelled a "campaign to belittle and disparage" him.

[54] In June 1946, Chifley announced that Makin would be appointed as Australian Ambassador to the United States, a decision that had been expected since December 1945, while also elevating the position in rank from resident minister.

[55][56][57] He retained his Cabinet posts until the 1946 election, reportedly because Chifley was unsure whether his desired successor would replace Makin.

[58] The United States ambassadorship was a position of great importance in the gathering Cold War atmosphere of the post-war years, atop a rapidly-expanding Australian presence in Washington.

The teetotal Makin found the cocktail party circuit "arduous", and although he acknowledged the opportunities for more informal diplomacy, resented the limitations of the demanding social calendar on his home life.

[67][68] While still a Member of Parliament in 1961 he authored a book with brief biographies of all leaders of the Federal Parliamentary Labor Party until that time.