The film grew out of a massive attempt by Twentieth Century-Fox to duplicate its earlier, unprecedented success with The Sound of Music by producing three expensive, large-scale musicals over a period of three years, Doctor Dolittle and Star! being the others. Unfortunately, film attendance as a whole was down and all three films' box-office performance reflected this. All were released amid massive pre-release publicity and all lost equally massive amounts of money for the studio (though "Dolly" was in the box office top 5 for the year of its release). The result was that several top studio executives lost their jobs, and the studio itself went into such dire financial straits that it only produced one picture for the entire calendar year of 1970. In truth, Fox would never recoup its losses until a highly successful theatrical reissue of "The Sound of Music" in early 1973.

The Harmonia Gardens sequence (where the song "Hello Dolly" is performed) took an entire month to shoot.

The large fountain in the Harmonia Gardens set was reused in The Towering Inferno. It can be seen in the top floor restaurant. It gets knocked over by the water and kills the bartender played by Gregory Sierra.

The original Broadway production of "Hello Dolly!" opened at the St. James Theater on January 16, 1964 and ran for 2844 performances, setting a Broadway longevity record. "Hello Dolly!" also won the 1964 Tony Awards for the Best Musical and Best Score. The original Broadway production is the seventeenth longest running show ever.

The original design of Barbra Streisand's gold-beaded gown shown in the Harmonia Gardens scene weighed 40 pounds and cost $8,000. Twice during rehearsals, she tripped over its 2.5-foot train. Other dancers also tripped over it during rehearsal, so the train was taken off the dress. The train is shown intact when Streisand starts down the stairs, but later it disappears.

The scenes set in turn-of-the-last-century Yonkers, New York, were actually filmed a few miles up the Hudson River, in Garrison New York. Yonkers was recreated by putting false fronts on the existing buildings of the small village. The final wedding scene and reprise were shot at the Trophy Point monument and overlook of the United States Military Academy in West Point, New York.

The set for the Harmonia Gardens filled an entire sound stage at Fox Studios and occupied three levels: a dance floor, a main section that surrounded the dance floor and an upper mezzanine. The Harmonia Gardens sequence took an entire month to shoot.

The singing voice of Irene Molloy was provided by Gilda Maiken and Melissa Stafford.

The song "Love Is Only Love", which Barbra Streisand as Dolly sings in her bedroom before the Harmonia Gardens scene, was not in the stage production of "Hello, Dolly". "Love Is Only Love" was written by Jerry Herman for the Broadway musical "Mame" but cut before that show's opening. The song occurred in the story as Mame Dennis tries to explain falling in love to her pre-teen nephew Patrick.

The train shown in the final shot is from the Strasburg Rail Road, an active steam museum short line still in existence today. The "Hello Dolly" car is open to the public.

When director George Roy Hill heard about the turn-of-the-century New York set constructed for the film, he wanted to use the set to film a brief sequence in which Butch Cassidy and the Sundance Kid and Etta Place visit the Big Apple. The producers were proprietary about the set, and didn't want it to appear in another movie. 20th Century Fox, however, allowed Hill to take still photographs of his stars Paul Newman, Robert Redford and Katharine Ross on the set, surrounded by the extras (who appear it the old-time, tinted photos as city crowds) which were used in a montage sequence that served as a transition between the U.S. West and Bolivia sections of the movie.