Initial reviews of the film were thoroughly mixed. Bosley Crowther of The New York Times wrote, "There is not an abundance of subtlety or the lately familiar Hitchcock bent toward significant and colorful scenery in this obviously low-budget job." Crowther called the "slow buildups to sudden shocks" reliably melodramatic but contested Hitchcock's psychological points, reminiscent of Krafft-Ebing's studies, as less effective. While the film did not conclude satisfactorily for the critic, he commended the cast's performances as "fair". British critic C. A. Lejeune was so offended that she not only walked out before the end but permanently resigned her post as film critic for The Observer. Other negative reviews stated, "a blot on an honorable career", "plainly a gimmick movie", and "merely one of those television shows padded out to two hours." Positive reviews stated, "Anthony Perkins' performance is the best of his career ... Janet Leigh has never been better", "played out beautifully", and "first American movie since Touch of Evil to stand in the same creative rank as the great European films." A good example of the mix is the New York Herald Tribune's review, which stated, "... rather difficult to be amused at the forms insanity may take ... keeps your attention like a snake-charmer."
The public loved the film, with lines stretching outside of theaters as people had to wait for the next showing. This, along with box office numbers, led to a reconsideration of the film by critics, and it eventually received a very large amount of praise. It broke box-office records in Japan and the rest of Asia, France, Britain, South America, the United States, and Canada, and was a moderate success in Australia for a brief period. It was the most profitable black-and-white sound film ever made, and Hitchcock personally realized well in excess of $15 million (about $120m today). He then swapped his rights to Psycho and his TV anthology for 150,000 shares of MCA, making him the third largest shareholder in MCA Inc., and his own boss at Universal, in theory; however, this did not stop them from interfering with his later films. Psycho was, by a large margin, the most profitable film of Hitchcock's career, earning over $12 million for the studio on release, and $15 million by the end of the year. Hitchcock's second most profitable was Family Plot ($7,541,000), and third place was a tie between Torn Curtain (1966) and Frenzy (1972), each earning $6,500,000. Around the time of the run's end, the film had grossed $32 million in domestic theaters.
In the United Kingdom, the film shattered attendance records at the London Plaza Cinema, but nearly all British critics panned it, questioning Hitchcock's taste and judgment. Reasons cited for this were the critics' late screenings, forcing them to rush their reviews, their dislike of the gimmicky promotion, and Hitchcock's expatriate status. Perhaps thanks to the public's response and Hitchcock's efforts at promoting it, the critics did a re-review, and the film was praised. TIME switched its opinion from "Hitchcock bears down too heavily in this one" to "superlative" and "masterly", and Bosley Crowther put it on his Top Ten list of 1960.
The Catholic Legion of Decency gave the film a B rating, meaning "morally objectionable in part".
Psycho was criticized for making other filmmakers more willing to show gore; three years later, Blood Feast, considered to be the first "splatter film", was released. Psycho's success financially and critically had others trying to ride its coattails. Inspired by Psycho, Hammer Film Productions launched a series of mystery thrillers including The Nanny (1965) starring Bette Davis and William Castle's Homicidal (1961) was followed by a slew of more than thirteen other splatter films.
On the review aggregator website RottenTomatoes.com, Psycho holds a 'Certified: Fresh' score of 96%, with the critical consensus stated as, "Infamous for its shower scene, but immortal for its contribution to the horror genre. Because Psycho was filmed with tact, grace, and art, Hitchcock didn't just create modern horror, he validated it".