Joseph Cook was born in Staffordshire in England on 7 December 1860 to William and Margaret (Fletcher) Cooke. At the age of nine he started work in the mines as a pit boy. He read and studied to make up for his lack of education. By 1885 Cook was earning a living as a railway worker and married a local schoolteacher, Mary Turner, on 8 August 1885. On Christmas Eve that year emigrated to Australia. After the couple's first child was born in 1886, Mary Cook joined him in Lithgow, New South Wales, where both her husband and her brother worked in the coalmines. The transformation from pit boy to Prime Minister is a remarkable one, though Joseph Cook shares it with one other Australian Prime Minister, Andrew Fisher.

Joseph Cook became Labor Member for Hartley in the New South Wales parliament in 1891, and three years later was a minister in George Reid's Free Trade government.  He became a Free Trade member of the first federal parliament in 1901, and in 1909 was Defence Minister in Alfred Deakin's Fusion government. Joseph Cook led a busy life, he worked in the mines and was an active unionist and was studying to become a Methodist minister, as well as learning typing, shorthand and book-keeping. In 1888, a few months after the Cooks' second son, Albert, was born, Joseph Cook became general secretary of the union.

He was an avowed republican and a member of the Land Nationalisation League, a group campaigning for a single tax on landowners. Cook was a member of the defence committee coordinating the 1890 maritime strike when a third son, Joseph William, was born. In May 1891, Cook became president of the Lithgow branch of the Labor Electoral League, forerunner of the Labor Party and at the election the following month, he won the local seat of Hartley in the New South Wales parliament. Two years later, on 17 October 1893, hard work, drive and ambition were rewarded when Cook was elected leader of the New South Wales parliamentary Labor Party. The third annual conference in March 1894 had adopted the solidarity pledge, but Cook refused to commit himself to accept Caucus rule and resigned. He stood as Independent Labour at the July 1894 election.

When GH Reid became Premier in August 1894, Cook joined the Free Trade Party and became Postmaster-General in the Reid government. Though he and the new Premier were very different, Cook liked and admired Reid. The two men shared a deep commitment to reasoned choice as fundamental to democracy. By the time their fourth son, John Hartley, was born in 1897, Joseph and Mary Cook had bought their own house in central Lithgow. A daughter, Annette, was born the following year.

When the Reid government was returned in 1898, Cook became Minister for Mines and Agriculture. He was a diligent and sound administrator and his four ministerial years were productive, and he enforced high standards in both portfolios. In Agriculture, he achieved firm quarantine regulations and help for farmers in eradicating diseases, and appointed William Farrer to the new position of government wheat experimentalist.

Joseph Cook was not an ardent federationist and voted against the first referendum in 1898, but campaigned throughout mining areas for the 'yes' vote in the 1899 referendum. When the Reid government fell in September 1899, Cook remained a busy representative for his electorate. In 1900 the Cooks' sixth child, Winifred, was born.

At George Reid's insistence, Cook stood for the House of Representatives seat of Parramatta at the first federal election in March 1901. He won this seat and joined Reid's Free Trade Opposition in the first Commonwealth parliament. After their seventh child, Cecil, was born in 1902, the family moved to Sydney.

He had achieved a reputation as a shrewd and hardworking parliamentarian, and a master of parliamentary strategy. Like Reid, Cook saw the Labor Party as sectional and socialist, was equally critical of the Protectionist governments of Edmund Barton and Alfred Deakin, and was sceptical of the cooperation between Deakin and Labor leader JC Watson which led to Watson becoming Prime Minister in April 1904. Despite their shared views, when Reid formed government in August 1904, he did not make Cook a minister. Cook was, however, elected deputy leader of the Free Trade Party the next year.

In 1906 Cook was unopposed at the December election. The family's ninth child, Constance was born that year and, in 1908, the family moved to Baulkham Hills in Sydney. That year Cook's consistency was rewarded. A week before Labor withdrew support from Deakin on 13 November 1908 and Andrew Fisher took government, George Reid resigned from the Free Trade Party. This removed the key obstacle to a coalition of non-Labor groups, and Cook became the new leader of the Free Trade Party.

Under Cook's leadership, the Free Trade Party joined Alfred Deakin's Liberals in an anti-socialist "fusion".  For Cook and Deakin, arguments over defence policy dominated the rocky path to coalition. Cook observed that the Liberal leader 'nails his flag to the mast of compulsory training. I nail mine to the mast of increased naval subsidy'. Unlike Deakin, Cook saw no need for an Australian navy, arguing Australia had more to lose from British naval defeat than Britain itself: "It means for them white dominance; it means for us brown-coloured".

By May 1909 the three non-Labor groups had hammered out an historic agreement. Cook's Anti-Socialists, Deakin's Liberals and John Forrest's 'Corner' together built the enduring Labor and non-Labor coalition structure that has shaped Australian parliaments since.

Defence was the key concern of the final session of the third parliament. The Defence Act 1909, provided for a compulsory military training scheme. Deakin's aim was achieved in a defence agreement with Britain that included the establishment of an Australian navy. With the support of the Opposition, construction of the flagship, the battle cruiser HMAS Australia, began the same year.

In January and February 1910, Cook was host to British Field-Marshal Lord Kitchener, who was visiting at the Fusion government's request to advise on Australian defence. With Germany developing its military power and an aggressive stance, both the United States and Britain had increased their own capabilities. The "Great White Fleet" visit in 1908, part of President Theodore Roosevelt's show of United States naval strength, had been a huge success in Australia. Kitchener's visit had the same effect.An amendment to the Defence Act in January 1911 implemented most of the recommendations in Kitchener's report, including the establishment six months later of a military training institution like West Point - the Royal Military College at Duntroon.

At the general election on 13 April 1910, voters returned a Labor government, and ten days later Andrew Fisher was again sworn in as Prime Minister. The Fisher government had a comfortable majority in both Houses - a first in the Australian parliament's short history. The Fusion Party, renamed the Liberal Party, remained in Opposition for three years. Cook was a key figure in establishing the organisational structure of the party and in shaping its 'anti-socialist' policies in opposing the Labor Party. Though he was a man of little magnetism, Cook's sense of purpose attracted attention when he was in attack mode. His response to the spending program in the government's 1912 budget was published in the Sydney Mail as the 'financial carnival'.

With Alfred Deakin's health in obvious decline, he resigned the leadership of the parliamentary Liberal Party on 20 January 1913. In a contest with John Forrest, Cook was elected leader by one vote.Cook opened the Liberal's election campaign on 3 April 1913 with a policy speech drawing its weight not from a positive Liberal program, but from an almost ferocious anti-Labor stance. Among his 'socialist' targets were Labor's industrial relations changes, the proposed land tax and the maternity benefit. At the election on 31 May 1913, Cook's Liberals won government by a single seat. In 1913, Cook replaced Deakin as Leader of the Liberal Party opposition and in June of that year became the Prime Minister following the general election.

On 8 June 1914 Cook sought and obtained a double dissolution of parliament from Governor-General R.C. Munro-Ferguson, after the Senate had twice refused to pass the Government Preference Prohibition Bill. At the subsequent general election on 5 September 1914, Andrew Fisher's Labor Party won convincingly, gaining majorities in both the House of Representatives and the Senate. Cook's term as Prime Minister ended formally on 17 September when Fisher took office.In Opposition from September 1914, Cook and his Liberal Party fully supported the war policies of Fisher's and subsequently Hughes' Labor governments.

When "Billy" Hughes left the Labor Party in 1916 Cook brought the Liberal Party into a merger with Prime Minister Hughes' National Labor group, forming the Nationalist Party on 7 February 1917. Cook became Deputy Prime Minister under Hughes.

He resigned from parliament on 11 November 1921 to take up an appointment as Australian High Commissioner in London. He retained this position until his retirement on 10 May 1927. Joseph Cook returned to Australia in 1927 and in 1928-29 he headed the Royal Commission into South Australia as affected by Federation.

He died in Sydney in 1947.