A group of scientists are working on a serum called Death One, which reanimates the dead. When Dr. Alan Holder (Robert Marius) and his assistant Norma experiment on a human corpse, the corpse becomes a zombie, prompting Dr. Holder to resign from the project. As he prepares to surrender the serum to waiting military officers, a small group of criminals ambush the center; all but one are killed, and the surviving criminal manages to abscond with Death One. During a chase, the container with the serum is shot out of his hand and breaks; as he tries to pick it back up, he accidentally touches the serum. He flees to the Sweet River Resort and settles in Room 4. General Morton (Mike Monty) promises Dr. Holder that he and his men will capture the criminal. By the time the soldiers catch up to him, however, he has already succumbed to the disease, but not before infecting a bellhop and killing a maid before finally cutting off his own hand in a failed attempt to stop the spread of the infection. General Morton orders the patrons and staff killed and buried in a mass grave, and condemns the resort; the criminal's remains are delivered to him and his two right-hand men, Sergeant Tracey (Bruno Mattei) and Sergeant Cheney (Claudio Fragasso), and burned. As Dr. Holder and Norma fear, the ashes quickly infect the air, killing an entire flock of birds passing by.
Meanwhile, a trio of GIs on vacation are on the lookout for some girls to make out with during their holiday; they find several on a nearby bus. Among the bus's passengers are Nancy (Ulli Reinthaler), Carol (Marina Loi), Lia (Deborah Bergamini), Suzanna (Mari Catotiengo), Jane, Jane's boyfriend Tom, and the bus driver, Joe.
Not too far away, a tourist named Patricia (Beatrice Ring) and her boyfriend Glenn discover the dead birds and are promptly horrified as the birds reanimate and attack, with Glenn being pecked and clawed repeatedly. The birds then assault the bus while the GIs attempt to extricate everyone from it, but not before Lia gets bitten. Patricia and Glenn stop at a nearby garage but are forced to flee when a zombie wielding a machete attacks Patricia and the garage goes up in smoke when she sets the zombie aifre.
The GIs and the bus party make a stop at Sweet River Resort, which is now deserted. The men find a crate full of guns left behind by the soldiers and set about fortifying the place. One of the GI's, Bo (Massimo Vanni) and Carol take one of the abandoned cars from the resort's parking lot and drive off to look for some help.
When their car breaks down, Carol goes looking for some water but is attacked and mauled by the zombies. Bo tries and fails to save her and is forced to flee when more zombies emerge from the lake. He eventually joins up with Patricia and Glenn. On the way to Santa Monica Hospital, Glenn dies and reanimates as a zombie on a bridge. During the resulting confrontation with the living dead, Bo is killed, but Patricia escapes with her life. Meanwhile, Dr. Holder and his team start work on an antidote to counter the effects of Death One as General Morton's men start to eradicate the zombies.
Back at the hotel, Jane and Tom go to the kitchen to look for some food but are ambushed and killed by a zombie head that had been resting in the freezer. Lia reanimates, kills and devours Susanna and almost kills Nancy before being thrown off the balcony and killed. Kenny (Deran Sarafian) and Roger (Ottaviano Dell'acqua) encounter Patricia as she arrives to try to break the news about Bo's demise, but the living dead start swarming the hotel. Kenny, Roger, Patricia, Nancy, and Joe kill as many zombies as they can before fleeing.
The next morning after crossing the river, the survivors are met by some of General Morton's soldiers, who kill Joe. The other four escape as the final stage of General Morton's zombie eradication begins and Dr. Holder expresses his worries that the infection of the atmosphere may not be restricted to the island. Arriving at the nearby Santa Monica Hospital, the four encounter a pregnant woman in labor. As Nancy helps deliver the newborn, Patricia engages in a final deathmatch against the zombie Glenn and beheads him, while Kenny and Roger have another run-in with General Morton's cleanup crew. Nancy is killed by the newborn, who turns out to be a zombie, and Kenny, Roger, and Patricia escape to find more zombies waiting for the kill. They make it to a helicopter, but only Kenny and Patricia are able to escape with their lives. Roger is attacked by the zombies while trying to join them and is subsequently killed by the cleanup crew. To Patricia's horror, the zombies have taken over; Blue Heart, the DJ who provided commentary for much of the film, even dedicates his next record to "all the undead around the world", having been infected himself. Upon hearing the broadcast, Kenny decides to return to the island, assuring Patricia that he intends to save what's left of humanity from the zombies.Deran Sarafian as Kenny
Beatrice Ring as Patricia
Ottaviano Dell'acqua as Roger
Massimo Vanni as Bo
Ulli Reinthaler as Nancy
Marina Loi as Carol
Deborah Bergamini as Lia
Rossella Drudi developed most of the script of Zombi 3 without credit. The film only credits Drudi's husband, Claudio Fragasso, who co-authored the screenplay. Their script set the film in the Philippines as it was a cheap and convenient location to shoot. Zombi 3 was originally announced as a 3D film, but the film was never released in this format. Director Lucio Fulci went to the Philippines along with his daughter Camilla Fulci, and spent six weeks shooting Zombie 3.
After completing filming, he would later state that he "didn't finish making Zombie 3, but the reason wasn't anything to do with illness [...] there were arguments and so, I finished off an hour and a quarter of the film". Fulci stated that he couldn't get the script changed, which he deemed to be "dreadful", and modified it with his daughter. Claudio Fragasso stated that Fulci simplified his screenplay and shot a seventy-minute film which shocked producer Franco Gaudenzi. Fragasso went on to state that after the final editing of the film, it had a running time of one hour and ten minutes, but felt like a slow montage, and was cut down further to 50 minutes. Two opposing views were given for Fulci leaving the film, the first being an illness that left him unable to film and the second being that he was having disputes with producers.
Producer Gaudenzi was worried about the film, and had second unit director (Bruno Mattei) brought in to work on the production with Fragasso in order to complete it. Mattei had been in the Philippines at the time filming Strike Commando 2. Both Fragasso and Mattei make cameos in the film as soldiers who are putting a corpse into an incinerator. Both Fragasso and Mattei worked on new scenes. As they could not get the main actors again, their scenes became subplots. Mattei claimed that he shot about 40% of the film, including all the early scenes in the film and the scenes in which the men are dressed in white anticontamination suits.
Zombi 3 was released in Italy on July 29, 1988 The film was released in a severely edited form in Italy. Other films were released internationally promoting themselves as a sequel to Zombi 2. These include Andrea Bianchi's Burial Ground released as Zombi III: Nights of Terror and Return of the Zombies as Zombi 3. Zombi 3 is regarded as the official follow-up to Zombi 2.
In the United States, Zombi 3 was released in 2002 by Media Blasters. The cut version of the film shown in Italy provided the majority of the master for this DVD. In the United Kingdom, the film was released under the title of Zombie Flesh Eaters 2 as part of Vipco's Vault of Horror collection. Vipco later re-issued Zombi 3 as part of their budget 'Screamtime Collection'.
In December 2015 UK label 88 Films released Zombi 3 as part of their Italian Collection on Blu-ray with a reversible cover with one side titled Zombie Flesh Eaters 2 and the other side titled Zombi 3.
From retrospective reviews, Video Watchdog commented that the film had "slow patches" but plenty of exciting (and extremely gory) highlights throughout" The review also commented on Stefano Mainetti's score that "certainly helps things along". Writing in The Zombie Movie Encyclopedia, academic Peter Dendle said, "Most of the movie is a quilt of scenes and motifs shamelessly pasted together from Dawn of the Dead and Return of the Living Dead, but fast pacing and continuous shooting help distract from the absence of plot or character development." Dread Central included the film in their top ten list of best viral outbreak films.