The seventh child of Henrietta Catherine (Graham) and Daniel Malthus, Robert Malthus grew up in The Rookery, a country house in Westcott, near Dorking in Surrey. Petersen describes Daniel Malthus as "a gentleman of good family and independent means... [and] a friend of David Hume and Jean-Jacques Rousseau". The young Malthus received his education at home in Bramcote, Nottinghamshire, and then at the Warrington Academy from 1782. Warrington was a dissenting academy, then at the end of its existence, and it closed in 1783; Malthus continued for a period to be tutored by Gilbert Wakefield who had taught him there.

Malthus entered Jesus College, Cambridge in 1784. There he took prizes in English declamation, Latin and Greek, and graduated with honours, Ninth Wrangler in mathematics. His tutor was william Frend. He took the MA degree in 1791, and was elected a Fellow of Jesus College two years later. In 1789, he took orders in the Church of England, and became a curate at Oakwood Chapel (also Okewood) in the parish of Wotton, Surrey.

Malthus argued in his Essay (1798) that population growth generally expanded in times and in regions of plenty until the size of the population relative to the primary resources caused distress:

In 1799 Malthus made a European tour with william Otter, a close college friend, travelling part of the way with Edward Daniel Clarke and John Marten Cripps, visiting Germany, Scandinavia and Russia. Malthus used the trip to gather population data. Otter later wrote a Memoir of Malthus for the second (1836) edition of his Principles of Political Economy. During the Peace of Amiens of 1802 he travelled to France and Switzerland, in a party that included his relation and Future wife Harriet. In 1803 he became rector of Walesby, Lincolnshire.

On 13 March 1804, Malthus married Harriet, daughter of John Eckersall of Claverton House, near Bath. They had a son and two daughters. His firstborn, son Henry, became vicar of Effingham, Surrey, in 1835, and of Donnington, Sussex, in 1837; he married Sofia Otter (1807–1889), daughter of Bishop william Otter, and died in August 1882, aged 76. His middle child, Emily, died in 1885, outliving her parents and siblings. The youngest, Lucille, died unmarried and childless in 1825, months before her 18th birthday.

In 1805 Malthus became Professor of History and Political Economy at the East India Company College in Hertfordshire. His students affectionately referred to him as "Pop" or "Population" Malthus.

In terms of public policy, Malthus was a supporter of the protectionist Corn Laws from the end of the Napoleonic Wars. He emerged as the only Economist of note to support duties on imported grain. He changed his mind after 1814. By encouraging domestic production, Malthus argued, the Corn Laws would guarantee British self-sufficiency in food.

Although government in Britain had regulated the prices of grain, the Corn Laws originated in 1815. At the end of the Napoleonic Wars that year, Parliament passed legislation banning the importation of foreign corn into Britain until domestic corn cost 80 shillings per quarter. The high price caused the cost of food to increase and caused distress among the working classes in the towns. It led to serious rioting in London and to the "Peterloo Massacre" (1819) in Manchester.

At the end of 1816 the proposed appointment of Graves Champney Haughton to the College was made a pretext by Randle Jackson and Joseph Hume to launch an attempt to close it down. Malthus wrote a pamphlet defending the College, which was reprieved by the East India Company in 1817. In 1818 Malthus became a Fellow of the Royal Society.

Ricardo corresponded with Malthus from 1817 and his Principles. He was drawn into considering political economy in a less restricted sense, which might be adapted to legislation and its multiple objectives, by the thought of Malthus. In his own work Principles of Political Economy (1820), and elsewhere, Malthus addressed the tension, amounting to conflict, he saw between a narrow view of political economy, and the broader moral and political plane. Leslie Stephen wrote:

In 1820 Malthus published Principles of Political Economy. 1836: Second edition, posthumously published. Malthus intended this work to rival Ricardo's Principles (1817). It, and his 1827 Definitions in political economy, defended Sismondi's views on "general glut" rather than Say's Law, which in effect states "there can be no general glut".

Malthus was a founding member of the Political Economy Club in 1821; there John Cazenove tended to be his ally, against Ricardo and Mill. He was elected in the beginning of 1824 as one of the ten royal associates of the Royal Society of Literature. He was also one of the first fellows of the Statistical Society, founded in March 1834. In 1827 he gave evidence to a committee of the House of Commons on emigration.

After Ricardo's death in 1823, Malthus became isolated among the younger British political economists, who tended to think he had lost the debate.It is now considered that the different purposes seen by Malthus and Ricardo for political economy affected their technical discussion, and contributed to the lack of compatible definitions. For Example, Jean-Baptiste Say used a definition of production based on goods and services and so queried the restriction of Malthus to "goods" alone.

McCulloch was the Editor of The Scotsman of Edinburgh; he replied cuttingly in a review printed on the front page of his newspaper in March, 1827. He implied that Malthus wanted to dictate terms and theories to other economists. McCulloch clearly felt his ox gored, and his review of Definitions is largely a bitter defence of his own Principles of Political Economy, and his counter-attack "does little credit to his reputation", being largely "personal derogation" of Malthus. The purpose of Malthus's Definitions was terminological clarity, and Malthus discussed appropriate terms, their definitions, and their use by himself and his contemporaries. This motivation of Malthus's work was disregarded by McCulloch, who responded that there was nothing to be gained "by carping at definitions, and quibbling about the meaning to be attached to" words. Given that statement, it is not surprising that McCulloch's review failed to address the rules of chapter 1 and did not discuss the definitions of chapter 10; he also barely mentioned Malthus's critiques of other Writers.

Malthus died suddenly of heart disease on 23 December 1834, at his father-in-law's house. He was buried in Bath Abbey. His portrait, and descriptions by contemporaries, present him as tall and good-looking, but with a cleft lip and palate. The cleft palate affected his speech: such birth defects had occurred before amongst his relatives.

The vast bulk of continuing commentary on Malthus, however, extends and expands on the "Malthusian controversy" of the early 19th century.