Marshall grew up in the London suburb of Clapham and was educated at the Merchant Taylor's School, Northwood, and St John's College, Cambridge, where he demonstrated an aptitude in mathematics, achieving the rank of Second Wrangler in the 1865 Cambridge Mathematical Tripos. Although he wanted, at the behest of his father, to become a clergyman, his success at Cambridge University led him to an academic career. He became a professor in 1868 specializing in political economy. He desired to improve the mathematical rigor of economics and transform it into a more scientific profession. In the 1870s he wrote a small number of tracts on international trade and the problems of protectionism. In 1879, many of these works were compiled into a work entitled The Pure Theory of Foreign Trade: The Pure Theory of Domestic Values. In the same year (1879) he published The Economics of Industry with his wife Mary Paley Marshall.

Although Marshall took economics to a more mathematically rigorous level, he did not want mathematics to overshadow economics and thus make economics irrelevant to the layman. Accordingly, Marshall tailored the text of his books to laymen and put the mathematical content in the footnotes and appendices for the professionals. In a letter to A.L. Bowley, he laid out the following system:

(1) Use mathematics as shorthand language, rather than as an engine of inquiry. (2) Keep to them till you have done. (3) Translate into English. (4) Then illustrate by examples that are important in real life (5) Burn the mathematics. (6) If you can’t succeed in 4, burn 3. This I do often."

Marshall had been Mary Paley's professor of political economy at Cambridge and the two were married in 1877, forcing Marshall to leave his position as a Fellow (college) of St John's College, Cambridge, in order to comply with celibacy rules at the university. He became the first principal at University College, Bristol, which was the institution that later became the University of Bristol, again lecturing on political economy and economics. He perfected his Economics of Industry while at Bristol, and published it more widely in England as an economic curriculum; its simple form stood upon sophisticated theoretical foundations. Marshall achieved a measure of fame from this work, and upon the death of William Jevons in 1882, Marshall became the leading British economist of the scientific school of his time.

Marshall returned to Cambridge, via a brief period at Balliol College, Oxford during 1883–4, to take the seat as Professor of Political Economy in 1884 on the death of Henry Fawcett. At Cambridge he endeavored to create a new tripos for economics, a goal which he would only achieve in 1903. Until that time, economics was taught under the Historical and Moral Sciences Triposes which failed to provide Marshall the kind of energetic and specialized students he desired.

Marshall began his seminal work, the Principles of Economics, in 1881, and spent much of the next decade at work on the treatise. His plan for the work gradually extended to a two-volume compilation on the whole of economic thought. The first volume was published in 1890 to worldwide acclaim that established him as one of the leading economists of his time. The second volume, which was to address foreign trade, money, trade fluctuations, taxation, and collectivism, was never published.

He served as President of the first day of the 1889 Co-operative Congress.

Over the next two decades he worked to complete the second volume of his Principles, but his unyielding attention to detail and ambition for completeness prevented him from mastering the work's breadth. The work was never finished and many other, lesser works he had begun work on - a memorandum on trade policy for the Chancellor of the Exchequer in the 1890s, for instance - were left incomplete for the same reasons.

His health problems had gradually grown worse since the 1880s, and in 1908 he retired from the university. He hoped to continue work on his Principles but his health continued to deteriorate and the project had continued to grow with each further investigation. The outbreak of the First World War in 1914 prompted him to revise his examinations of the international economy and in 1919 he published Industry and Trade at the age of 77. This work was a more empirical treatise than the largely theoretical Principles, and for that reason it failed to attract as much acclaim from theoretical economists. In 1923, he published Money, Credit, and Commerce, a broad amalgam of previous economic ideas, published and unpublished, stretching back a half-century.

From 1890 to 1924 he was the respected father of the economic profession and to most economists for the half century after his death, the venerable grandfather. He had shied away from controversy during his life in a way that previous leaders of the profession had not, although his even-handedness drew great respect and even reverence from fellow economists, and his home at Balliol Croftin Cambridge had no shortage of distinguished guests. His students at Cambridge became leading figures in economics, including John Maynard Keynes and Arthur Cecil Pigou. His most important legacy was creating a respected, academic, scientifically founded profession for economists in the future that set the tone of the field for the remainder of the 20th century.

Having died aged 81 at his home in Cambridge, Marshall is buried in the Ascension Parish Burial Ground. The library of the Department of Economics at Cambridge University (The Marshall Library of Economics) as well as the University of Bristol Economics department are named for him. His home, Balliol Croft, was renamed Marshall House in 1991 in his honour when it was bought by Lucy Cavendish College, Cambridge.

Marshall is considered to be one of the most influential economists of his time, largely shaping mainstream economic thought for the next fifty years, and being one of the founders of the school of neoclassical economics. Although his economics was advertised as extensions and refinements of the work of Adam Smith, David Ricardo, Thomas Robert Malthus and John Stuart Mill, he extended economics away from its classical focus on the market economy and instead popularized it as a study of human behavior. He downplayed the contributions of certain other economists to his work, such as Leon Walras, Vilfredo Pareto and Jules Dupuit, and only grudgingly acknowledged the influence of Stanley Jevons himself.

Marshall's influence on codifying economic thought is difficult to deny. He popularized the use of supply and demand functions as tools of price determination (previously discovered independently by Cournot); modern economists owe the linkage between price shifts and curve shifts to Marshall. Marshall was an important part of the "marginalist revolution;" the idea that consumers attempt to adjust consumption until marginal utility equals the price was another of his contributions. The price elasticity of demand was presented by Marshall as an extension of these ideas. Economic welfare, divided into producer surplus and consumer surplus, was contributed by Marshall, and indeed, the two are sometimes described eponymously as 'Marshallian surplus.' He used this idea of surplus to rigorously analyze the effect of taxes and price shifts on market welfare. Marshall also identified quasi-rents.

Marshall's brief references to the social and cultural relations in the "industrial districts" of England were used as a starting point for late twentieth century work in economic geography and institutional economics on clustering and learning organizations.

Gary Becker (b. 1930), the 1992 Nobel prize winner in economics, has mentioned that Milton Friedman and Alfred Marshall were the two greatest influences on his work.