The film opens with a group of strangely colored humanoids emerging from tanks in a laboratory. The scientists responsible for these creations, Dr. Collie and Nain among others, are congratulated by their employer, Lord Jaguar, who plans to make these "Bio-Humans" into the strongest fighters on Earth. Despite warnings from his cousin, Men-Men, Jaguar laughs maniacally as one of his unfinished bio-humans wags his furry tail in his tank.
As Mr. Satan has not yet paid Android 18 the prize money she demanded for letting him beat her in the 25th World Martial Arts Tournament, she begins smashing Satan House up, particularly his undeserved prizes from the tournament. Mr. Satan, cowering, tries to tell 18 that he has not gotten the money yet, but she does not believe him, and continues to ransack his home. His screams of fright are heard by Kuririn, Marron, Trunks, and Son Goten, who are waiting outside.
Mr. Satan is visited by Men-Men, who claims to be the cousin of the champion's old martial arts rival Jaguar. It seems that Jaguar is blackmailing Mr. Satan into visiting his laboratory island to fight his Bio-Warriors, as Jaguar is the only other person who knows of Mr. Satan's bed wetting secret when he was younger. Mr. Satan agrees, and departs to Mei Queen Castle with Men-Men, followed by 18, Trunks, and Goten.
Upon arriving, Mr. Satan is coldly greeted by Jaguar, who sets up a tournament for him to fight the Bio-Warriors, but when they demonstrate their incredible fighting abilities, they are more than Mr. Satan can handle, Goten, Trunks, and 18 intervene. Goten and Trunks are then confronted by a familiar face: Maloja, the Priest from Natade Village whom they met in the previous movie, Broly - Second Coming.
Enraged, Jaguar reveals his greatest weapon: a Super Bio-Warrior. But when Trunks and Goten see the Super Bio-Warrior, they recognize him as none other than the Legendary Super Saiyan himself, Broly. They confront the priest, who tells them that he sold Broly's frozen blood to Jaguar, and that the Super Bio-Warrior is Broly's clone. Trunks and Goten prepare to destroy Bio-Broly before he can be revived, but he had sensed the attack, which awakened Broly's Saiyan instincts. He breaks out of stasis, only to be drenched in the bio-liquid and turns into a horribly deformed, slime covered bio-mutant, giving him the name Bio-Broly. Meanwhile, Maloja is taking all the money in Jaguar's safe, only for the liquid to come behind him and kill him as he tries to ward it off with an evil banishment prayer.
Jaguar commands Bio-Broly to attack Mr. Satan, but 18 intervenes at the last minute, only to get pounded by the Bio-Saiyan. Just before Bio-Broly can kill Satan, Goten and Trunks intervene and save him in time. They then attack Bio-Broly head-on, and prove to be an equal match for the Bio-Saiyan, until Goten abandons the battle to save some trapped scientists from the flooding and dangerous bio-liquid that will absorb anything with a different genetic structure to its own and grow stronger.
As Bio-Broly pounds Trunks around, 18 recovers and tries to stop him, but she too is beaten. Just before Bio-Broly can kill her, Kuririn shows up in time and rescues 18, but Bio-Broly finds them both and almost kills them. Goten and Trunks then fight Bio-Broly again, but they get seriously pounded, and Bio-Broly almost kills Goten until Trunks lures the menace away.
Trunks manages to lure Bio-Broly away from his battered friends, and then fires an upside-down Finish Buster at him, only for it to miss. It seems that Trunks is doomed, until a tank that had been hit by the Finish Buster ruptures, causing bio-liquid to shower on Bio-Broly and supposedly melt him. Unfortunately, this only makes the bio-liquid more powerful, and it soon starts to flood the entire island, seemingly unstoppable. Goten, Trunks, Kuririn and 18 manage to get as many people as they can out of the lab, including the reluctant Jaguar and Men-Men, who want to die shamefully along with their deadly creations, but Trunks rescues them anyway, and Mr. Satan manages to escape by jumping into the water.
To everyone's surprise, the bio-liquid seems to be solidifying by touching the sea water, so Trunks, Goten, and Kuririn use a triple Kamehameha to blast the water by the island so high that the entire island is flooded with sea water, which solidifies all the bio-liquid. Unfortunately, the celebrations are cut short when Bio-Broly emerges from the sea as a giant. However, as fast as Bio-Broly emerges, he then turns to stone, due to having been drenched in sea water. Seeing their chance, Goten and Trunks blast the gigantic Bio-Broly statue into smithereens, ridding the universe of Broly for good.
Mr. Satan emerges from the sea water, calling for help. Laughing, 18 says that she will help him if he promises to pay her 100,000,000 zeni. Fuming, Satan swims off. In Other World, Son Goku is informed that Broly is causing trouble in Hell. Along with Pikkon, Goku is sent to stop Broly, after he finishes an enormous meal.
- Masako Nozawa as Son Goku & Son Goten
- Takeshi Kusao as Trunks
- Miki Ito as Android 18
- Mayumi Tanaka as Kuririn
- the late Daisuke Gori as Mr. Satan
- the late Tomiko Suzuki as Marron & Nan
- Naoki Tatsuta as Bubbles & Jaga Bada
- Chafurin as Maloja
- Masaharu Sato as Dr Collie
- Bin Shimada as Bio-Broly
- Joji Yanami as the Narrator
- Kara Edwards as Goten
- Laura Bailey as Trunks
- Meredith McCoy as Android 18 & Marron
- Sonny Strait as Kuririn
- Chris Rager as Mr. Satan
- Bill Townsley as Lord Jaguar
- Robert McCollum as Maloja
- Christopher Sabat as Dr Collie
- Caitlin Glass as Nan
- Sean Schemmel as Goku
- Vic Mignogna as Bio-Broly
- Kyle Hebert as the Narrator
- This is first movie where Android 18 plays an active role, she briefly appears along with her brother in Dragon Ball Z movie 7, but does not play a large role. This is also the only movie where she fights alongside her husband, Kuririn.
- This is the first movie in which Marron makes an appearance. Also Meredith McCoy voices her instead of Laura Bailey.
- Kuririn, Trunks and Goku are the only characters to appear in all three Broly movies. Trunks appears as a baby in the first Broly movie and Goku appears as a baby in the movies. Nonetheless, he did have a speaking dialogue and physical appearance in body format. This is the only Broly movie where Kuririn actually fights against Broly.
- The scene showing Trunks' private part was edited out in most English versions, and when he gives Bio Broly the middle finger, it is turned into a fist. When this film airs on TV, Trunks' face is crudely (with no resizing and rather low quality) zoomed in on.
- When Bio-Broly is getting covered by the Culture Fluid, Trunks is shown with darker-than-normal colored eyebrows.
- This is the first time Trunks uses the Kamehameha on-screen.
- Right before they fire the Kamehameha to spread seawater over the island, Kuririn has a golden aura instead of the regular white ki aura which manifests for most humans when they gather up their energies.
- This is the last movie to have the main antagonist's name on the title in the American version.
- From this movie until Dragon Ball: Yo! Son Goku and His Friends Return!!, the main villains do not speak (or at the most say only a single word). A theme of the later movies involve the antagonists' speech level going down. Bojack gets few lines in Dragon Ball Z: Bojack Unbound, Broly only gets one line aside from "Kakarot!" in Dragon Ball Z: Broly - Second Coming, Bio-Broly does not speak (except yelling "Kakarot!" when emerging from the sea), neither does Janemba (except for when he is in his first form, in which case he only says his own name) in Fusion Reborn, and neither does Hirudegarn in Wrath of the Dragon.
- Although the film states that Broly had been killed as a direct result of being blasted into the Sun from Second Coming, the video game Dragon Ball: Raging Blast 2 disagrees with it by revealing that Broly has not only survived the action, but also became even stronger and gained a Super Saiyan 3 transformation as a result.
- The 21st Shunsuke Kikuchi music package for the franchise starts here. The cues were designated "M19XX" codes, and this package would make its series debut in Buu's Mutiny.
- The only DBZ film not to have Goku or Gohan as the main hero, and the first one in which Piccolo does not appear. Also the first film since Movie 6 (Return of Cooler) that Vegeta did not have a speaking role.
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