The son of Sir Michael Hicks Beach, 8th Baronet, whom he succeeded in 1854, he was born in London in 1837, and educated at Eton and Christ Church, Oxford, where he graduated with a first class in the school of law and modern history. In 1864 he was returned to parliament as a Conservative for East Gloucestershire. During 1868 he acted both as parliamentary secretary to the Poor Law Board and as under-secretary for the Home Office. In 1874 he was made Chief Secretary for Ireland, and was included in the Cabinet in 1877. From 1878 to 1880 he was Secretary of State for the Colonies. In 1885 he was elected for West Bristol, and became Chancellor of the Exchequer and Leader of the House of Commons. After Gladstone's brief Home Rule Ministry in 1886 Hicks Beach entered Lord Salisbury's next Cabinet again as Irish secretary, making way for Lord Randolph Churchill as leader of the House; but troubles with his eyesight compelled him to resign in 1887.
From 1888 to 1892 Sir Michael Hicks Beach returned to active work as President of the Board of Trade, and in 1895 Goschen being transferred to the Admiralty he again became Chancellor of the Exchequer. In 1899 he lowered the fixed charge for the National Debt from twenty-five to twenty-three millions, a reduction imperatively required, apart from other reasons, by the difficulties found in redeeming Consols at their then inflated price. When compelled to find means for financing the war in South Africa, he insisted on combining the raising of loans with the imposition of fresh taxation; and besides raising the income-tax each year, he introduced taxes on sugar and exported coal (1901), and in 1902 proposed the reimposition of the registration duty on corn and flour which had been abolished in 1869 by Lowe. The sale of his Netheravon estates in Wiltshire to the War Office in 1898 occasioned some acrid criticism concerning the valuation, for which, however, Sir Michael himself was not responsible.
On Lord Salisbury's retirement in 1902 Sir Michael Hicks Beach also left the government. He accepted the chairmanship of the Royal Commission on Ritualistic Practices in the Church, and he did valuable work as an arbitrator; and though when the fiscal controversy arose he became a member of the Free-food League, his parliamentary loyalty to Balfour did much to prevent the Unionist free-traders from precipitating a rupture. In 1906 he was raised to the peerage as Viscount St Aidwyn. In 1915 he was made an Earl.