Jack Nicholson was considered for the lead male role of Allie Fox which in the end was cast with Harrison Ford. Nicholson withdrew from the film partially because he could not watch his Los Angeles Lakers basketball team from Belize where much of the movie was to be filmed.
During casting River Phoenix was passed on several times for the role of Charlie Fox for being too old (he was 15). When no age-appropriate Charlie could be found, Phoenix's audition tape was brought in again to director Peter Weir and, impressed by the actor, he decided to put the age issue aside and give Phoenix the job.
While filming this movie River Phoenix would use his off time roaming the city of Belize, and took full advantage of the potent cocaine available in the country. At this time with the cocaine abuse, he also developed an addiction to alcohol. This is all according to John Glatt's biography of Phoenix called Lost in Hollywood.
In an 'Entertainment Weekly' magazine article entitled 'Regarding Harrison' from a 1992 interview, star Harrison Ford said of this movie: "It's the only film I have done that hasn't made its money back. I'm still glad I did it. If there was a fault with the film, it was that it didn't fully enough embrace the language of the [source] book [by Paul Theroux]. It may have more properly been a literary rather than a cinematic exercise. But I think it's full of powerful emotions".
Due to principal photography on this picture, star Harrison Ford and director Peter Weir both famously missed the 1986 Academy Awards Ceremony, for which they had both had been nominated for Witness (1985), in the Best Actor and Best Director categories respectively. Witness (1985) went on to win two Oscars, for Best Film Editing and Best Original Screenplay, after being nominated for eight, including Best Picture.
Show-business trade paper 'Variety' described this movie as "a modern variation of Swiss Family Robinson". Many critics, reviewers and audiences have compared The Mosquito Coast (1986) with Johann David Wyss' classic "Swiss Family Robinson" (1812) novel.
First of two collaborations of actors River Phoenix and Harrison Ford. The pair would work together again around three years later in Indiana Jones and the Last Crusade (1989). Phoenix played the younger version of Indiana Jones, in the film's opening flashback sequence, with Ford portraying the usual regular adult form of the character.
Peter Weir had planned to make the film with Jack Nicholson in the lead, and was already moving furniture into the production office when he was informed the funding had fallen through. Calling his agent, he asked for a "go" project into which he could step immediately as director. He was offered three - COCOON, THE MEAN SEASON and WITNESS - and chose WITNESS,
The trivia item below may give away important plot points.
The book's rather gruesome ending was toned down for the movie. In the book, Allie Fox finally collapses, after which he is eaten by vultures (creatures he despises throughout the book). In the movie, his character played by Harrison Ford slowly dies from his wounds.