Hackett's movie career began in 1950 for Columbia Pictures. with a 10-minute "World of Sports" reel called King of the Pins. The film demonstrated championship bowling techniques, with expert Joe Wilman demonstrating the right way and Hackett (in pantomime) exemplifying the wrong way. Hackett would not return to movies until 1953, after one of his nightclub routines attracted attention. With a rubber band around his head to slant his eyes, Hackett's "The Chinese Waiter" lampooned the heavy dialect, frustration, and communication problems encountered by a busy waiter in a Chinese restaurant: "No, we no have sprit-pea soup... We gotta wonton, we got eh-roll... No orda for her, juss orda for you!" The routine was such a hit that Hackett made a recording of it, and was hired to reprise it in the 1953 Technicolor musical Walking My Baby Back Home, produced by Universal-International.
Hackett was an emergency replacement for Lou Costello in 1954. Abbott and Costello were set to make a feature-length comedy Fireman, Save My Child, with a guest appearance by Spike Jones and His City Slickers. Several scenes had been shot with stunt doubles when Lou Costello was forced to withdraw due to illness. Universal-International salvaged the project by hiring Hugh O'Brian and Hackett to take over the Abbott and Costello roles; Jones and his band became the main attraction.
Hackett became known to a wider audience when he appeared on television in the 1950s and 1960s as a frequent guest on such talk shows as Jack Paar and Arthur Godfrey, telling brash, often off-color jokes, and mugging widely at the camera. During this era, he also appeared as a panelist on What's My Line?. Hackett also appeared many times on the game show Hollywood Squares, in the late 60's.
Hackett became widely known from his role in the 1963 box-office success It's a Mad, Mad, Mad, Mad World. After starring on Broadway in I Had a Ball, Hackett appeared opposite Robert Preston in the 1962 film adaptation of The Music Man. Children became familiar with him as lovable hippie auto mechanic Tennessee Steinmetz in Disney's The Love Bug (1968). He appeared as Art Carney's replacement on The Jackie Gleason Show, and in the 1958 film God's Little Acre. His later career was mostly as a guest on variety shows and prime time sitcoms such as Boy Meets World in its 4th season.
Throughout the 1970s Hackett appeared regularly doing TV ads for popsicles and yogurt.
His last film performance was reprising the voice of Scuttle, the goofy little seagull, in Disney's The Little Mermaid (1989) for the direct-to-video sequel The Little Mermaid II: Return to the Sea in 2000. Hackett also appeared in the short term comedy series Action which starred Jay Mohr as movie producer Peter Dragon. He played Dragon's uncle Lonnie. He appeared again with Mohr as a judge in the reality show Last Comic Standing. For his contribution to the motion picture industry, Hackett was given a star on the Hollywood Walk of Fame.
In April 1998, Hackett guest starred in an episode of LateLine called "Buddy Hackett." The episode focuses on a news broadcast paying tribute to Hackett following his death, only to discover that the report of his death was a mistake. Robert Reich and Dick Gephardt also appeared in the episode, paying tribute to Hackett.
Hackett's body was cremated.