Addison was born in Millstone, Wiltshire, but soon after his birth his father, Lancelot Addison, was appointed Dean of Lichfield and the Addison family moved into the cathedral close. He was educated at Charterhouse School, where he first met Richard Steele, and at The Queen's College, Oxford. He excelled in classics, being specially noted for his Latin verse, and became a fellow of Magdalen College. In 1693, he addressed a poem to John Dryden, and his first major work, a book of the lives of English poets, was published in 1694. His translation of Virgil's Georgics was published in the same year. Dryden, Lord Somers and Charles Montague, 1st Earl of Halifax, took an interest in Addison's work and obtained for him a pension of £300 to enable him to travel to Europe with a view to diplomatic employment, all the time writing and studying politics. While in Switzerland in 1702, he heard of the death of William III, an event which lost him his pension, as his influential contacts, Halifax and Somers, had lost their employment with the Crown.

Addison returned to England at the end of 1703. For more than a year he remained unemployed, but the Battle of Blenheim in 1704 gave him a fresh opportunity to distinguish himself. The government, specifically Lord Treasurer Godolphin, commissioned Addison to write a commemorative poem about the battle, and he produced The Campaign, which was received with such satisfaction that he was appointed Commissioner of Appeals in Halifax's government. His next literary venture was an account of his travels in Italy, Remarks on several parts of Italy, &c., in the years 1701, 1702, 1703, published in 1705 by Jacob Tonson. In 1705, with the Whigs in power, Addison was made Under-Secretary of State and accompanied Lord Halifax on a diplomatic mission to Hanover, Germany. A biography of Addison states: "In the field of his foreign responsibilities Addison's views were those of a good Whig. He had always believed that England's power depended upon her wealth, her wealth upon her commerce, and her commerce upon the freedom of the seas and the checking of the power of France and Spain."

Following the Duke of Marlborough's successful campaign of 1706, the Duke and George Stepney became the first English regents of the Anglo-Dutch condominium for governing the southern Netherlands. It was Stepney who formally took possession of the principality of Mindelheim in the Duke's name on 26 May, after the Battle of Ramillies. Upon Marlborough's return to London in November, Parliament accepted the Duke's request that a grant of £5,000 'out of ye Post-Office' be made in perpetuity to his heirs.

He wrote the libretto for Thomas Clayton's opera Rosamond, which had a disastrous premiere in London in 1707. In 1713 Addison's tragedy Cato was produced, and was received with acclamation by both Whigs and Tories. He followed this effort with a comedic play, The Drummer (1716).

In 1708 and 1709, Addison was a Member of Parliament for the borough of Lostwithiel. He was soon appointed secretary to the new Lord Lieutenant of Ireland, Lord Wharton. Under the direction of Wharton, he was an MP in the Irish House of Commons for Cavan Borough from 1709 until 1713. in 1710, he represented Malmesbury, in his home county of Wiltshire, holding the seat until his death in 1719.

He met Jonathan Swift in Ireland and remained there for a year. Later, he helped form the Kitcat Club and renewed his friendship with Richard Steele. In 1709, Steele began to publish the Tatler, and Addison became a regular contributor. In 1711 they started The Spectator. The first issue appeared on 1 March 1711. This paper, which was originally a daily, was published until 20 December 1714, interrupted for a year by the publication of The Guardian in 1713. His last publication was The Freeholder, a political paper, in 1715–16.

It is as an Essayist that Addison is remembered today. Addison began writing essays quite casually. In April 1709, his childhood friend, Richard Steele, started The Tatler. Addison contributed 42 essays to the Tatler while Steele wrote 188. Regarding Addison's help, Steele remarked, "when I had once called him in, I could not subsist without dependence on him". On 2 January 1711, The Tatler was discontinued. On 1 March 1711, The Spectator was published, and it continued until 6 December 1712. The Spectator was issued daily and achieved great popularity. It exercised an influence over the reading public of the time. Addison soon became the leading partner in The Spectator. He contributed 274 essays out a total of 555; Steele wrote 236. Addison also assisted Steele with the Guardian which began in 1713.

Addison wrote the popular church hymn "The Spacious Firmament on High", publishing it in The Spectator in 1712. It is sung either to the tune known as "London (Addison's)" by John Sheeles, written c. 1720, or to "Creation" by Franz Haydn, 1798.

The later part of Addison's life was not without its troubles. In 1716, he married Charlotte, Dowager Countess of Warwick, after working for a time as a tutor for her son. His political career continued, and he served as Secretary of State for the Southern Department from 1717 to 1718. His political newspaper, The Freeholder, was much criticized, and Alexander Pope, in An Epistle to Dr Arbuthnot, made him an object of derision, naming him "Atticus", and comparing him to an adder, "willing to wound, and yet afraid to strike." His wife was arrogant and imperious; his stepson, Edward Rich, was an unfriendly rake. Addison's shyness in public limited his effectiveness as a member of Parliament. He eventually fell out with Steele over the Peerage Bill of 1719. In 1718, Addison was forced to resign as Secretary of State because of his poor health, but he remained an MP until his death at Holland House, London, on 17 June 1719 (age 48). Addison was buried in Westminster Abbey. After his death, an apocryphal story circulated that Addison, on his deathbed, had sent for his wastrel stepson to witness how a Christian man meets death.

He wrote an essay entitled Dialogues on Medals which was translated to the French by eighteenth-century priest and Journalist Simon-Jérôme Bourlet de Vauxcelles (1733–1802). He also left an incomplete work, Of the Christian Religion.

The play was a success throughout the British Empire. It continued to grow in popularity, especially in the America, for several generations. It is cited by some historians as a literary inspiration for the American Revolution, being known to many of the Founding Fathers. General George Washington sponsored a performance of Cato for the Continental Army during the difficult winter of 1777-78 at Valley Forge. According to John J. Miller, "no single work of literature may have been more important than Cato" for the Leaders of the American revolution.

In 1789, Edmund Burke quoted the play in a letter to Charles-Jean-François Depont entitled Reflections on the revolution in France, saying that the French people may yet be obliged to go through more changes and "to pass, as one of our poets says, 'through great varieties of untried being,'" before their state obtains its final form. The poet referred to is Addison and the passage quoted is from Cato (V.i. II): "Through what variety of untried being, through what new scenes and changes must we pass!"

On 6 April 1808, a town in upstate New York, (Middletown) was renamed Addison, in his honor.

Thomas Macaulay wrote this generous tribute to Addison in 1866:

In 2005, an Austrian banker and collector named Albin Schram died, and in his laundry room a collection of a thousand letters was found, some of them of interest to historians. Two of them were written by Joseph Addison.

The action of the play involves the forces of Cato at Utica, awaiting the attack of Caesar immediately following his victory at Thapsus (46 BC). The noble sons of Cato, Portius and Marcus, are both in love with Lucia, the daughter of Lucius, an ally of Cato. Juba, Prince of Numidia, one of Cato's warriors, loves Cato's daughter Marcia. Meanwhile, Sempronius, a senator, and Syphax, a general of the Numidians, are conspiring secretly against Cato, hoping to prevent the Numidian army from supporting him. In the final act, Cato commits suicide, leaving his followers to make their peace with the approaching army of Caesar—an easier task after Cato's death, since he was Caesar's most implacable enemy.

"As a man, he may not have deserved the adoration which he received from those who, bewitched by his fascinating society, and indebted for all the comforts of life to his generous and delicate friendship, worshiped him nightly, in his favourite temple at Button’s. But, after full inquiry and impartial reflection, we have long been convinced that he deserved as much love and esteem as can be justly claimed by any of our infirm and erring race. Some blemishes may undoubtedly be detected in his character; but the more carefully it is examined, the more it will appear, to use the phrase of the old anatomists, sound in the noble parts, free from all taint of perfidy, of cowardice, of cruelty, of ingratitude, of envy. Men may easily be named, in whom some particular good disposition has been more conspicuous than in Addison. But the just harmony of qualities, the exact temper between the stern and the humane virtues, the habitual observance of every law, not only of moral rectitude, but of moral grace and dignity, distinguish him from all men who have been tried by equally strong temptations, and about whose conduct we possess equally full information." – Lord Macaulay