When The Wealth of Nations was finally published, David Hume consoled Smith that while it required too close a reading to become quickly popular, it would, by its "depth and solidity and acuteness" and its "curious facts", eventually attract the public. The publisher was less optimistic. The first edition, in two volumes and over a thousand pages, consisted of 500 copies selling for the standard price of £1 16s, for which Smith received the grand sum of £300 — this for the author of the well-known and highly regarded Theory of Moral Sentiments that had appeared in a new edition only two years earlier. Those 500 copies sold out in six months, a second edition was published two years later, and three others followed in the dozen years before his death in 1790. The book was translated during his lifetime into French, German, Italian, Danish, and Spanish, and received the imprimatur of success in the form of a lengthy abridgement. Some of the most eminent men of the time, across the political spectrum, declared themselves his disciple: Edmund Burke and Thomas Paine, Edward Gibbon and Richard Price, William Pitt and Lord North.

Part of the success of The Wealth of Nations has been attributed, ironically, to the fact that it was not altogether original. The term laissez faire, like political economy, was an import from France dating from the reign of Louis XIV, when a merchant is said to have pleaded with the king's minister, Louis-Baptiste Colbert, "Laissez-nous faire." Later popularised by the Physiocrats protesting against the highly regulated economy, it was imported into England where it retained its French form. (The term itself does not appear in The Wealth of Nations, although the concept obviously does.) Similarly, the "division of labour," the subject of the first chapter of the book, had its antecedents in Chambers's Cyclopaedia in 1728 (complete with the pin-factory example publicised by Smith); in the French Encyclopédie decades later (which borrowed it, with the same example); and in a book by Smith's friend, Adam Ferguson, Essay on the History of Civil Society, published only a few years before The Wealth of Nations.

The Victorian economist Walter Bagehot, an admirer of Smith, conceded that these terms and concepts were not novel and that the idea of free trade was "in the air," although not generally accepted or established. "On the contrary, it was a tenet against which a respectable parent would probably caution his son; still it was known as a tempting heresy and one against which a warning was needed." A later economic historian, Joseph Schumpeter (less well disposed to Smith), agreed that there was little original in The Wealth of Nations — not "a single analytic idea, principle, or method that was entirely new in 1776". It was a "great performance" deserving of success, Schumpeter conceded, but that success came, paradoxically, from Smith's limitations. "Had he been more brilliant, he would not have been taken so seriously. Had he dug more deeply, had he unearthed more recondite truth, had he used difficult and ingenious methods, he would not have been understood." But those were not his intentions or aspirations. "In fact he disliked whatever went beyond plain common sense. He never moved above the heads of even the dullest readers." He spoke their language, made them feel comfortable, and, most important, was "thoroughly in sympathy with the humours of his time". 

Among the "humours of his time" that endeared Smith to his readers (but not to Schumpeter) was the moral philosophy that infused his political economy. So far from seeing The Wealth of Nations as a refutation of The Theory of Moral Sentiments (as some later commentators have), contemporaries welcomed the new book as a complement to the old. Edmund Burke, having reviewed the first book glowingly when it appeared, was as admiring in his review of the second. Nor did the new book displace or supersede the old. The appreciative memoir of Smith by Dugald Stewart, written three years after Smith's death, devoted 26 pages to The Theory of Moral Sentiments and only 17 to The Wealth of Nations.