Admiral Kirk's defeat of Khan and the creation of the Genesis planet are empty victories. Spock is dead and McCoy is, seemingly inexplicably, being driven insane. Then an unexpected visit from Sarek, Spock's father, provides a startling revelation: McCoy is harboring Spock's living essence. With one friend alive and one not, but both in pain, Kirk attempts to help his friends by stealing the Enterprise and defying Starfleet's Genesis quarantine. But the Klingons have also learned of Genesis and race to meet Kirk in a deadly rendezvous.

William Shatner - Admiral Kirk

Leonard Nimoy - Capt. Spock

DeForest Kelley - Dr. Leonard McCoy

James Doohan - Capt. Scott

George Takei - Cmdr. Sulu

Walter Koenig - Cmdr. Chekov

Nichelle Nichols - Cmdr. Uhura

Merritt Butrick - Dr. David Marcus

Phil Morris - Trainee Foster

Scott McGinnis - Mr. Adventure

Robin Curtis - Lt. Saavik

Robert Hooks - Adm. Morrow

Carl Steven - Spock...Age 9

Vadia Potenza - Spock...Age 13

Stephen Manley - Spock...Age 17

Joe W. Davis - Spock at age 25

Paul Sorenson - Captain

Cathie Shirriff - Valkris

Christopher Lloyd - Cmdr. Kruge

Stephen Liska - Torg

John Larroquette - Maltz

David Cadiente - Klingon sergeant

Branscombe Richmond - Gunner 2

Phillip R. Allen - Capt. J.T. Esteban

Jeanne Mori - Helm

Bob K. Cummings - Klingon gunner 1

Mario Marcelino - Communications

Allan Miller - Alien

Sharon Thomas - Waitress

Conroy Gedeon - Civilian agent

James Sikking - Capt. Styles

Miguel Ferrer - First Officer

Mark Lenard - Ambassador Sarek

Katherine Blum - Vulcan child

Judith Anderson - Vulcan High Priestess

Gary Faga - Prison guard 1

Douglas Alan Shanklin - Prison guard 2

Grace Lee Whitney - Janice Rand

Harve Bennett - Flight recorder

Judi M. Durand - Space Dock controller

Teresa E. Victor - Enterprise computer

Frank Welker - Spock screaming

Charles Correll - Space Dock worker

Leonard Nimoy's character, Spock, died at the end of the previous movie. He agreed to reincarnate the character in exchange for directing the new movie.

The villains of the film were originally intended to be Romulans, but upper studio management wanted Klingons to be used since they were better-known enemies. By the time the decision was made, the Romulan ship was already made and they didn't want the expense of replacing it. Fortunately, the TV show had already established that the Klingons and Romulans had shared technologies and ships in the past (for exactly the same real-world cost-cutting reasons) so the idea of Klingons using a Romulan-style vessel was not a problem.

Production was endangered by the great fire at Paramount. William Shatner helped fight the fire and rescue a crewmember before firefighter reinforcements arrived.

When the Enterprise enters space dock at the beginning of the movie, just before Uhura comments on the Excelsior's appearance ("Would you look at that!"), another docked ship can be seen, in shadow, at the upper left corner of the screen. This ship is one of the alternative models that was considered for use as the Excelsior. This alternate model also makes several appearances in Star Trek: The Next Generation, usually as a wrecked ship or piece of space junk.

First Star Trek "episode" to be directed by a member of the Star Trek cast. This would later become commonplace on the various Trek TV series.

The self-destruct codes for the U.S.S. Enterprise apparently haven't been changed in decades, as they are identical to those in the original series episode "Let That Be Your Last Battlefield".

Scenes of Spock's final moments and his death from "Star Trek II - The Wrath of Khan" were reused as the engine room's flight recorder. The opening death sequence, funeral sequence, Spock's casket's landing spot, Spock's opening dialogue and opening were all reused from "Star Trek II: The Wrath of Khan" where they were all used at the end of that film.

Tribbles - a popular creature from the original TV series - make a cameo appearance during the bar sequence where McCoy tries to hire a ship.

The Excelsior was supposed to debut in Star Trek II and be identified as newly-promoted Capt. Sulu's first command. This plotline was dropped and Excelsior saved for this film. Sulu would finally take command of her in Star Trek VI. The ship design would be reused for the USS Enterprise-B in the movie Star Trek - Generations

In the earlier drafts of the screenplay, the Enterprise's auto destruct finished with the ship's engine core exploding, resulting in a massive matter/antimatter explosion, visible from the planet's surface. Harve Bennett later changed this to the primary hull exploding, and the secondary being destroyed in the planet's atmosphere, reasoning that an antimatter explosion would probably destroy the Klingon ship as well. However, a mix-up resulted in the ILM crew doing the sequence according to the earlier version. Bennett considered using this version in the final film, but asked ILM to redo it, this time saying it would make the scene afterwards look too much like the ending of Return of the Jedi. They saved money by re-using the footage from the initial sequence up to the point where the primary hull exploded, then started the new sequence just after.

The U.S.S. Grissom bridge was the U.S.S. Enterprise bridge rearranged with pink chairs, and the Bar where McCoy tries to charter the spaceflight is the Enterprise sickbay redressed.

The USS Excelsior's computer voice (heard in the turbolift when Scotty mutters "Up your shaft") was supplied by director Leonard Nimoy.

The scene in which Kirk stumbles into his chair after hearing of the death of his son was an improvisation by William Shatner, who was told by Leonard Nimoy to do whatever reaction Shatner wanted to do. Shatner has never told whether he meant to miss the chair and slip to the ground, or if he had meant to simply hit the seat hard but missed going backwards.

As in the previous Star Trek film, the movie includes the famous "Space, the final frontier" monologue, spoken by Spock. As in the previous film, the words have been changed slightly, referring to seeking out "new life forms" instead of just "new life". This was the final use of this modified version of the monologue.

The few Klingon phrases that James Doohan introduced in Star Trek: The Motion Picture was used by Marc Okrand as the basis for the Klingon language in this film. Okrand's Klingon language became a fully realized fictional language, and would be the basis for all future Klingon dialogue in future movies and television shows (as well as an obsession to become fluent in for hardcore Star Trek fans.)

The spacedock orbiting Earth is supposed to be five miles tall - making it easily observable from the surface. The actual model itself was 6 feet tall.

Chekov makes a remark in Russian to Scotty about Spock's quarters having been invaded. Translated, he is saying, "I'm not crazy! There it is."

Michael Eisner initially refused to let Leonard Nimoy direct the film, as he was under the mistaken impression that Spock's death was part of Nimoy's contract from the previous film, and that therefore, Nimoy didn't like the series or the part. He changed his mind when Nimoy assured him that this was not true.

To keep the secrecy, the name "Spock" was never used in the movie script, but instead the alias "Nacluv" (reverse of "Vulcan") was used.

The uniforms worn by the security guards are the same uniforms from Star Trek: The Motion Picture, but they're worn with the new red Starfleet uniforms, and a dark green turtleneck, which represents the security division.

This film marks the first appearances of the Excelsior class vessel, the Oberth class vessel (namely the USS Grissom), and the Klingon bird-of-prey. The models were reused as other, similar ships in numerous episodes of "The Next Generation" and "Deep Space Nine."

There was a debate during the writing of the script as to who should be killed by the Klingons - Saavik (Robin Curtis) or David Marcus (Merritt Butrick). It was eventually decided that Marcus should die as punishment for experimenting with protomatter in the Genesis matrix.

Continuity error: Arrangement of Kirk's duelling pistols on the wall in the background when Sarek and Kirk are talking in Kirk's home.

Revealing mistake: When Kirk and Kruge are fighting, a piece of the cliff breaks away and wiggles down the side of the cliff rather than falling like a rock.

Revealing mistake: During the opening sequence, you can see a highway with cars driving in the bottom left-hand corner of one of the scenes.

Continuity error: Chekov's clothes change after the Enterprise leaves the Spacedock facility. It was unlikely that he would have taken the time to change his clothes during a moment of crisis.

Crew or equipment visible: During the self destruction of the Enterprise, there's an explosion where a Klingon goes flying over the navigation console. When he lands, an arm can be seen helping him.

Revealing mistake: Obvious stunt double for Kruge during his fight with Kirk.

Continuity error: When the seal to Spock's quarters is broken, the Bridge displays of the ship and of Spock's quarters are based on the original Constitution-class vessels (from the TV show) and not the refitted movie version.

Continuity error: Phase of the Earth's Moon when the Enterprise arrives at space dock after the battle with Khan, and when Kirk steals the Enterprise.

Continuity error: When Kirk checks the video logs to find the keeper of Spock's katra, the timestamp reveals that Spock melded with McCoy on stardate 8128.78. The Wrath of Khan begins on stardate 8130.3.

Leonard Nimoy is credited as director in the opening credits, but is not included in the cast list.  There is a long gap between the name of William Shatner and DeForest Kelley, which lasts for the length of time Nimoy's name would have been displayed.

Some network broadcasts are noticably truncated. In particular, the scene where Kruge destroys the female mercenary for looking at the Genesis information is cut. The scene ends instead with the two characters expressing love for each other! The scene where McCoy refers to "that green-blooded son-of-a-bitch" is also censored.

An early ABC-TV broadcast had the flashbacks of Spock's Death and the opening scene of Captain Kirk on the Enterprise bridge cut for time constraints. Instead the opening fades in on Spock's tube being loaded for launch and then after the opening credits, it switches straight to the scenes between the freighter and the Klingon ship followed by the Enterprise's arrival at Earth.

On pan and scan VHS releases, the opening credits are "chyroned" in, looking compressed. This is done so the background picture would not be compressed.