Hayek felt that application of Keynes's policies would give too much power to the state and would lead to socialism. Professor Herbert Frankel later expanded on this perceived danger of Keynes's thinking, drawing on support from the work of Georg Simmel. Attacks on Keynes for lending support to socialism and excessive state control have remained popular from Libertarians and Austrian School Economists.

While Milton Friedman described The General Theory as 'a great book', he argues that its implicit separation of nominal from real magnitudes is neither possible nor desirable; macroeconomic policy, Friedman argues, can reliably influence only the nominal. He and other monetarists have consequently argued that Keynesian economics can result in stagflation, the combination of low growth and high inflation that developed economies suffered in the early 1970s. More to Friedman's taste was the Tract on Monetary Reform (1923), which he regarded as Keynes's best work because of its focus on maintaining domestic price stability.

Joseph Schumpeter was an economist of the same age as Keynes and one of his main rivals. He was among the first reviewers to argue that Keynes's General Theory was not a general theory, but was in fact a special case. He said the work expressed "the attitude of a decaying civilisation". After Keynes's death Schumpeter wrote a brief biographical piece called Keynes the Economist - on a personal level he was very positive about Keynes as a man ; praising his pleasant nature, courtesy and kindness. He assessed some of Keynes biographical and editorial work as among the best he'd ever seen. Yet Schumpeter remained critical about Keynes's economics, linking Keynes's childlessness to what Schumpeter saw as an essentially short term view. He considered Keynes to have a kind of unconscious patriotism that caused him to fail to understand the problems of other nations. For Schumpeter "Practical Keynesianism is a seedling which cannot be transplanted into foreign soil : it dies there and become poisonous as it dies."

Austrian School economic commentator and journalist Henry Hazlitt wrote a paragraph-by-paragraph refutation of The General Theory in his 1959 extensive critique of Keynesianism: The Failure of the New Economics. In 1960 he published the book The critics of Keynesian Economics where he gathered together the major criticisms of Keynes made up to that year.

Libertarian philosopher and Austrian School economist Murray Rothbard wrote a strongly worded critique of Keynes entitled Keynes the Man. Rothbard accused Keynes of being an intellectual lightweight, fixated on simple short-term solutions to complex long-term problems, obsessed with his own ego and influence, and one of the most destructive statist intellectuals of the 20th century.

Keynes was on occasion heard making statements which could be perceived as racist by Americans: for example, he would use the word "niggers" to refer to Negroes in casual conversations. However, this term was used neutrally in Britain at that time, and was almost certainly not an expression of negative feelings, as when, for example, he wrote to Duncan Grant that “the only really sympathetic and original thing in America are the niggers, who are charming”. He also wrote that there was a "beastliness in the Russian nature” as well as "cruelty and stupidity”, and other comments which may be construed as anti-Russian. Some critics, such as Rothbard, have sought to infer that Keynes had sympathy with Nazism or that he was anti-Semitic. Keynes's private letters express portraits and descriptions some of which can be characterised as anti-Semitic, while others as pro-Semitic.

These allegations have been roundly rejected by Keynes' supporters. Professor Gordon Fletcher writes that "the suggestion of a link between Keynes and any support of totalitarianism cannot be sustained". Once the aggressive tendencies of the Nazis towards Jews and other minorities became apparent, Keynes made clear his loathing of Nazism. As a lifelong pacifist he had initially favoured peaceful containment, yet he began to advocate for a forceful resolution while many conservatives were still arguing for appeasement. After the war started he roundly criticised the left for losing their nerve to confront Hitler.

Keynes had many Jewish friends, including Isaiah Berlin and Piero Sraffa. Keynes several times used his influence to help his Jewish friends, most notably when he successfully lobbied for Wittgenstein to be allowed residency in Great Britain explicitly in order to rescue him from being deported to Nazi-occupied Austria. Keynes was, furthermore, a supporter of Zionism, serving on committees supporting the cause. Scholars have suggested the occasional negative and stereotypical portraits of Jewish people expressed in Keynes's private letters reflect clichés current at the time that he accepted uncritically, rather than reflecting any ill feeling towards Jews.

Keynes has been characterised as being indifferent or even positive about inflation. Keynes had indeed expressed a preference for inflation over deflation, saying that if one has to choose between the two evils its "better to disappoint the rentier" than to inflict pain on working class families. However Keynes was consistently adamant about the need to avoid inflation where possible.