Y Tu Mamá También was well received by critics upon its original release. The review aggregator website Rotten Tomatoes reported that 92% of critics gave the film positive reviews, based upon a sample of 130. On Metacritic, which assigns a numbered rating out of 100 based on reviews from mainstream critics, the film received an average score of 88 based on 35 reviews, indicating "Universal Acclaim". Roger Ebert gave the film four stars out of four, and referred to it as "One of those movies where 'after that summer, nothing would ever be the same again.' Yes, but it redefines 'nothing.'"
Y Tu Mamá También won the Best Screenplay Award at the Venice Film Festival. It was also a runner-up at the National Society of Film Critics Awards for Best Picture and Best Director and earned a nomination for Best Original Screenplay at the 2003 Academy Awards. The film made its U.S. premiere at the Hawaii International Film Festival.
It was released without a rating in the U.S. because a market-limiting NC-17 was unavoidable. The MPAA's presumed treatment of this film based on the graphic depiction of sex and drug use – in comparison to its much more accepting standards regarding violence – prompted critic Roger Ebert to question why movie industry professionals were not outraged: "Why do serious film people not rise up in rage and tear down the rating system that infantilizes their work?"
In 2001, Alfonso and Carlos Cuarón sued the Mexican Directorate of Radio, Television, and Cinema (RTC) for the film’s 18-and-over rating, which they considered illegal political censorship. They took legal action to expose the government-controlled ratings board, prompting its transformation into an autonomous organization free of government involvement and political influence. The brothers sought a 12-and-over rating with encouraged parental guidance because the film was aimed toward a teenage audience. The 18+ rating was administered due to the film’s strong sexual content involving teens, drug use, and explicit language. They claimed the ratings board was operating illegally by denying parents the responsibility to choose what their child can watch, violating fundamental legal rights in Mexico.