The film combines anime footage from the direct-to-video Megazone 23 (1985) and Super Dimensional Cavalry: Southern Cross (1984), which was the second part of the Robotech television series.
A new "happy ending" was animated because the original ending of Megazone 23 (1985) was considered too downbeat.
The film was only in very limited theatrical release in Texas and was released on home video in a small number of international markets.
According to Carl Macek, Robotech: The Untold Story was supposed to be a straight dub of Megazone 23 Part I, but because the Cannon Films executives were not happy with the original ending, Macek rewrote the script, spliced in footage from Super Dimensional Cavalry Southern Cross, and commissioned Idol Co. Ltd. to animate a completely new ending (which was later included in the laserdisc release of Megazone 23 Part II). Because Megazone 23 was shot in 35mm film and Southern Cross was shot in 16mm film (which was the standard for TV series titles at the time), visual inconsistencies were very noticeable on the big screen.
The movie did a test run in Texas, where it failed. However, it was a surprise hit in some countries like Argentina. Harmony Gold let their license to Megazone 23 expire a few years later.
The events of this movie were originally intended to take place during the events of the Macross Saga when the SDF-1 was in deep space. This had to be changed when the film was re-edited with Southern Cross footage, which also altered its place in the time-line. Originally Colonel Andrews was intended to be a younger version of Colonel Edwards who would have appeared as a regular character in the aborted Robotech II: The Sentinels. In the book Robotech Art 3, by Carl Macek, Edwards' original name was B.D. Edwards. During the time of the Southern Cross segment, Edwards would have been elsewhere (as a crew-member aboard the SDF-3 in Sentinels). This necessitated the change of the movie character to B.D. Andrews. Edwards' initials were changed to T.R.