Entertaining Mr. Sloane has generally been overshadowed by what are now considered Orton's more mature and more clearly "farcical" plays, Loot and What the Butler Saw. However, when Orton's first full-length play premiered, eminent British playwright Terence Rattigan called it (in a letter to Orton quoted by Lahr) "the most exciting and stimulating first play ... that I've seen in thirty (odd) years' playgoing." And while reviewing the 1981 Off-Broadway revival of the play, New Yorker theatre critic Edith Oliver, while admitting the superiority of Orton's later efforts, exclaimed, "but what a debut!"

As with all of Orton's purposefully shocking plays, Entertaining Mr. Sloane aroused violently mixed reactions in its initial production. Some reviews referred to him as a bright new figure in the theatre world while others blanched at the play's amorality, noting that the play's homicide (Kemp's death) was unaccompanied by any moral judgment. Still others, like the anonymous critic for the London Times, tried to ride the fence, saying "the coarseness is sometimes offensive but it is characteristic of the offensive people who use it; it is theatrically valid." As Lahr pointed out in Prick up Your Ears, Orton "enjoyed the hostility as much as the praise, bad reviews featuring [in his scrapbook] as prominently as raves." The most negative review for the initial production at the New Arts Theatre came from one W. A. Darlington, in the conservative Daily Telegraph, who asserted that "not for a long time have I disliked a play so much as I disliked Joe Orton's Entertaining Mr. Sloane. I feel as if snakes had been writhing round my feet." As Lahr reported, Orton responded to this vitriol by writing his own mock condemnation of the play for the "Letters to the Editor" section of The Daily Telegraph, assuming the pseudonym of Mrs. Edna Welthorpe and declaring that she was "nauseated by this endless parade of mental and physical perversion." As the war of opinions raged, Rattigan saw in Orton's first play the style of William Congreve (Love for Love) and Oscar Wilde (The Importance of Being Earnest) Rattigan put up half the money for a transfer from the production's small, fringe venue at the New Arts to the Wyndham Theatre in the fashionable West End. There, Darlington reviewed the play a second time and found the characters still "shameless and repulsive in the extreme" but grudgingly admitted that his interest was this time "held throughout" (as quoted by Lahr).

Though the play continued to be very controversial during its run at the Wyndham, this major West-End production made Orton an overnight sensation. His play was soon slated for publication as the best new play of the year, and Orton was frequently labeled the year's most promising playwright. As Lahr summarized in his biography, "Orton, who had been surviving on three pounds a week until his first royalty check, found his weekly earnings to be as much as 239 pounds. The play was sold to Pans in August, and the next year to Spain, the United States, Israel, and Australia. It would be made into a film and a television play Orton had arrived in the style of his comedy—with a vengeance." As Lahr further pointed out, Orton "relished the scandal" that Entertaining Mr Sloane had provoked because it "proved the comic truth of his play, that the culture hid its violence behind a show of propriety."

The first American production of Entertaining Mr. Sloane opened on Broadway in October of 1965, attracting large preview audiences and the approval of established playwrights such as Edward Albee (Who's Afraid of Virginia Woolf?), Tennessee Williams (Cat on a Hot Tin Roof), and Peter Shaffer (Equus). The reviews for the American debut, however, were largely negative. Norman Nadel for the World Telegram and Sun said the play had "the sprightly charm of a medieval English cesspool," while John McClain of the New York Journal American suggested (as quoted by Lahr) that "if this is [England's] best play of any year they are in serious trouble." Howard Taubman of the New York Times called it "a singularly unattractive play." The production closed after thirteen performances. But the outraged Taubman continued his indictment of the play even after it closed, writing an essay in the Sunday New York Times that labeled Entertaining Mr. Sloane "nihilistic" and (in a blatant self-contradiction) "too insignificant to merit further belaboring." This prompted a response in the same paper a week later from Orton's director, Alan Schneider, who expressed confidence in the play's "ultimate vitality and durability in the history of contemporary drama."

The American vindication of Entertaining Mr. Sloane came in 1981 when an Off-Broadway revival succeeded where its earlier Broadway production had failed. New York Times reviewer Mel Gussow called the revival a "blissfully perverse comedy of bad manners," concluding that "today, posthumously, Orton's reputation is secure." Edith Oliver wrote in the New Yorker that this "first of Joe Orton's high comedies of lowlife" was "a minor classic." Referring to its 1965 Broadway flop, she added, "one wonders how so many people in New York could have failed to recognize its quality at once." And Robert Asahina, writing for the Hudson Review concluded that "Entertaining Mr. Sloane is still an insightful commentary on the sexual and social role confusion that is considerably more widespread now than when it was written."

Orton's first produced play has survived all of its controversial productions and continues to be revived in theatres around the world. Clearly less farcical than Loot and What the Butler Saw, Entertaining Mr. Sloane is now considered less typical of his style than Orton's last two major plays but still "Ortonesque" with provocative content and style.