Rod Steiger spoke in the southern dialect consistently for the duration of filming.

Rod Steiger was asked by director Norman Jewison to chew gum when playing the part. He resisted at first but then grew to love the idea,and eventually went through 263 packs of gum during the shooting of the film.

Sidney Poitier insisted that the movie be filmed in the north because of troubles that other productions filmed in the south had had when using black actors, including Hurry Sundown which had recently been shot in Louisiana (hence the selection of Sparta, Illinois for the location filming). Nevertheless, the filmmakers and actors did venture briefly into Mississippi for the outdoor scenes at the cotton plantation, because there was no similar cotton plantation in Illinois that could be used.

According to Norman Jewison and Haskell Wexler on the DVD commentary, they originally wanted to use "Lil' Red Ridin' Hood" by Sam the Sham and The Pharaohs in the movie, and this is the song Ralph Henshaw (Anthony James) was dancing to during filming. Unable to license Sam the Sham's song, "Foul Owl on the Prowl" was substituted, composed by Quincy Jones and performed by Boomer & Travis (better known as Owens Boomer Castleman and Michael Martin Murphey).

Due to the assassination of civil rights activist Martin Luther King (April 4, 1968), the presentation of the Best Picture Oscar for this film was postponed for two days from Monday April 8th to Wednesday April 10, 1968. (see also - The Life of Emile Zola and Raging Bull).

Frequently cited as Sidney Poitier's favorite of all the films he's done.

In 2007, the American Film Institute ranked this as the #75 Greatest Movie of All Time. It was the first inclusion of this film on the list.

Mississippi was eventually ruled out as a location due to the existing political conditions. Sparta, Illinois, was selected as the location, and the town's name in the story was changed to Sparta so that local signs would not need to be changed. The greenhouse was added to an existing home and filled with $15,000 worth of orchids.

Set in a hot Mississippi summer but filmed during autumn in Illinois, many of the actors had to keep ice chips in their mouths (and spit them out before takes) to prevent their breath from appearing on camera during the night scenes.

The movie's line "They call me Mister Tibbs!" was voted as the #16 movie quote by the American Film Institute

The movie's line "They call me Mister Tibbs!" was voted as the #76 of "The 100 Greatest Movie Lines" by Premiere in 2007.

The same locomotive is used in the opening and closing scenes to carry Virgil in and out of town - Gulf Mobile and Ohio locomotive #103.

The scene that took place at the sheriff's house featured dialog that came out of improvisations between Sidney Poitier and Rod Steiger.

The slapping scene between Det. Tibbs and Endicott was shot in just two takes, and the slaps the characters made to each other's faces were real, according to a detailed account Norman Jewison, provided in 2011.

Virgil tibbs arrives in Sparta, and subsequently leaves town, via the old Gulf, Mobile and Ohio Railroad (GM&O). This anchors the films setting in the deep south, and in Mississippi in particular. Yet, ten years earlier the GM&O had suspended all passanger service south of Saint Louis, MO; which Sparta, IL was and is. However, The GM&O had merged the Alton & Southern Railroad (which operated service between Saint Louis and Chicago). Therefore, filming of the operating train station scenes where Tibbs boards the train, as well as the long shot closing credits scenes, were completed at Alton, IL, about 75 miles north of Sparta. Careful viewing of the rail station scene early in the film between Tibbs and Chief Gillespie were at the "Sparta, IL" station but the Sparta station was clearly closed down.