The film version of the novel was made in 1963 and starred Marlon Brando as Ambassador Harrison Carter MacWhite. The Ugly American received mixed reviews and was completely overwhelmed by a number of better films that year. The film won no Golden Globes and neither won nor was nominated for an Oscar. It did poorly at the box office, not being among the year's top 25 grossing films of 1963.
The screenplay was written by Stewart Stern, and the film was produced and directed by George Englund. The film was shot mainly in Hollywood, with Thailand serving as the inspiration for the background sceneries. Parts of the film were also shot on locations in Bangkok, Thailand, including at Chulalongkorn University, one of the leading institutes of higher learning of the country. Upon release, the film garnered generally positive reviews from critics. Review aggregator Rotten Tomatoes reports that 80% of critics have given the film a positive review, with a rating average of 6.1/10.
Kukrit Pramoj, a Thai politician and scholar, was hired as a cultural expert/advisor to the film and later played the role of Sarkhan's Prime Minister "Kwen Sai". Later on, in 1975, he, in fact, did become the 13th Prime Minister of Thailand. Probably because of this, the word "Sarkhan" has entered the Thai language as a nickname of Thailand itself, often with a slight self-deprecating or mocking tone.
- Marlon Brando as Ambassador Harrison Carter MacWhite
- Eiji Okada as Deong
- Sandra Church as Marion MacWhite
- Pat Hingle as Homer Atkins
- Arthur Hill as Grainger
- Jocelyn Brando as Emma Atkins
- Mom Rajawongse Kukrit Pramoj as Prime Minister Kwen Sai
- Judson Pratt as Joe Bing
- Reiko Sato as Rachani, Deong's Wife
- George Shibata as Munsang
- Judson Laire as Senator Brenner
- Philip Ober as Ambassador Sears
- Yee Tak Yip as Sawad, Deong's Assistant
- Carl Benton Reid as Senator at Confirmation Hearing
Critical reaction and political discussion
The New York Times reported that Brando “moves through the whole picture with authority and intelligence,” and the New York Daily News said it was “one of Brando’s best performances.” But the negative view was reflected by the critic in Time Magazine who wrote that Brando “attempts an important voice but most of the time he sounds like a small boy in a bathtub imitating Winston Churchill,” and called it a “lousy picture.” 
Of twenty-three reviews examined by one scholar, fourteen were positive, five negative, and four neutral or mixed. Brando had given interviews where he questioned American Cold War politics, and some reviewers agreed, but few of these reviews mentioned that the film was set in a country very much like Vietnam. Only a few mentioned the point that, as the Dallas Morning News put it, one should “not assume that nationalism is inevitably anti-American,” and the New Republic was unusual in adding that “American blindness ... has driven many people particularly Asians, towards communism.” Some called Senator Brenner the real “ugly American” and objected to his McCarthyite tactics. The New York Post wrote that the film presented the dilemma that when Americans supported dictators, the Communists “make common revolutionary cause with the downtrodden.” Many East Coast reviews, however, objected to the film’s “oversimplification” of the issues. The Washington Post said it was “nothing more than a western about the bad guys and the good guys.”