Evans was born in 1787, in Moig, County Limerick, Ireland. Educated at Woolwich Academy he followed his elder brother Richard (1782–1847) into the military, joining the East India Company's forces in 1800 before volunteering for the British Army in India in 1806. He obtained an ensigncy in the 22nd Regiment of Foot in 1807 then exchanged into the 3rd Light Dragoons in order to take part in the Peninsular War. He was sent on the expedition to the United States of 1814 during the War of 1812 under Major General Robert Ross. Evans was quartermaster general to Ross at the Battle of Bladensburg on 24 August 1814, and during the Burning of Washington, as well as at the Battle of North Point on 12 September 1814, where Ross was killed. Evans was actively involved in the New Orleans campaign at the conclusion of the War of 1812. He was the only British Army officer present at the Royal Navy 'small boat action' on Lake Borgne, and was wounded at the battle of New Orleans.

Returning to the European war with the restoration of Emperor Napoleon I, Evans was present at the battle of Quatre Bras on 16 June 1815 and the battle of Waterloo on 18 June 1815. Evans commanded the British Legion, which volunteered to assist Isabella II of Spain in the First Carlist War. During the Crimean War he commanded the 2nd Division of the British Army. In 1853 he was given the colonelcy for life of the 21st Regiment of Foot (Royal North British Fusiliers) and promoted full general on 10 March 1861.

He served as a Member of Parliament for Rye in 1830, and from 1831 to 1832, and for Westminster from 1833 to 1841 and from 1846 to 1865. He was also awarded the Grand Cross of the French Legion of Honour. Evans died on 9 January 1870, and is buried in Kensal Green Cemetery, London.