Gibbs is a generally knowledgeable person and right-hand man to (Captain) Jack Sparrow, often providing the movie's cast as well as the audience with background information. He is deeply superstitious and makes frequent references to various causes of "bad luck" (e.g. having women on the ship or waking a sleeping man). He is also very fond of his rum, which he drinks from a leather flask. He takes a moment of silence to anyone who gets left behind (especially Jack) but gets over it quick enough. Gibbs is probably the only character who knows Jack Sparrow's history and has a great friendship with him, being one of the few people to admit he went to rescue Jack from Davy Jones' Locker because he missed him, and being the first one to agree to do so. He and Jack also share a handshake, and would say, in the first and third film "Take what you can - Give nothing back!" Writer Terry Rossio has said he actually considers Gibbs to be the most virtuous character in the series.
In the first film, Gibbs is first seen as a Royal Navy warrant officer (probably the boatswain) aboard the vessel carrying Governor Weatherby Swann and his young daughter Elizabeth Swann from England to Port Royal in the Caribbean. Gibbs is highly superstitious and fearful of the mere mention of pirates. When they come across a wrecked vessel (from which young Will Turner is rescued), Gibbs is the first to suggest it was attacked by pirates. He was likely correct, as Elizabeth witnessed the Black Pearl leaving the scene.
Sometime over the next eight years, Gibbs either leaves or is expelled from the Royal Navy. Despite his initial dread of pirates, he became good friends with one: the Black Pearl's former captain, Jack Sparrow. Jack's history is well-known to Gibbs, including his quest to regain the Pearl and seek revenge on his mutinous first mate, Hector Barbossa. He is also familiar with the curse that has afflicted the Black Pearl's crew and how to break it. He hasn't grown any less superstitious, however, and continually rambles on about what causes bad luck, such as bringing women aboard ships, as well as waking a man while he's sleeping.
Jack finds Gibbs sleeping among pigs in Tortuga after he and Will escape from Port Royal. They assemble a crew to man the stolen navy vessel Interceptor. After Jack falls behind during a confrontation with the pirates at Isa de Muerta, Gibbs assumes command, indicating he is now Jack's (more trustworthy) first mate.
Unfortunately, the Pearl quickly caught the Interceptor, and following a sea battle, the Interceptor was destroyed. Gibbs and the rest of the crew (along with Will and Elizabeth) were captured.
Back on Isla de Muerta, Elizabeth freed Gibbs and the crew from Pearl's brig and they took control of the ship. Although Elizabeth tried to convince Gibbs and the others to save Jack and Will, who were fighting Barbossa on the island, they set sail with the Pearl, telling Elizabeth that Jack owed them a ship. However, they later rescue Jack after he escapes the hangman's noose (with Will's assistance) in Port Royal. With Jack back in command of the Black Pearl, Gibbs stays on as second in command.
In the second film, Gibbs is still serving under Jack aboard the Black Pearl. In the beginning, he is singing Dead Man's Chest until Jack comes back with a drawing of the key to the Dead Man's Chest. Jack at first acts like he wants the crew to help him find the key and the chest but when Mr. Gibbs asks if the chest and key are what they are looking for, Jack always answers something like "No" or "You are not making any sense at all". Afterward, Gibbs, Jack, and the crew are captured by a cannibalistic native tribe after they beach the Black Pearl on the mysterious island of Pelegosto. Later Jack becomes chief of the Pelegostos which Gibbs describes Jack's actions of being chief is to actually stay alive from being eaten by the Cannibals, who think he is a god. But sometime later they narrowly escape, following Will Turner's arrival while searching for Jack. He still seems superstitious by nature, as shown when Jack reveals the Black Spot to Tia Dalma. Upon seeing the spot, Gibbs gasps in shock and, in a panic, performs a superstitious ritual where he spits, pats his chest three times, and spins in a circle. Pintel and Ragetti copy him. However, Gibbs seems less superstitious than before. At the movie's beginning, Gibbs sings the shanty, Dead Man's Chest aboard the Black Pearl before Jack arrives in a floating coffin. The song could be a prelude for the movie.
Gibbs accompanies Jack on his quest to find the Dead Man's Chest, containing the heart of Davy Jones, after Jack learns that Jones intends to collect a blood debt Jack owes him. When Jack goes ashore on Isla Cruces, he leaves Gibbs, Marty, Cotton, and the rest of the crew on the Pearl, which, according to the writers, is so they will be spared should the Kraken or Davy Jones attack. Instead, he takes the most dispensable crew members (James Norrington, Pintel, Ragetti, and Elizabeth Swann).
Gibbs is also among the few survivors after the Pearl is destroyed by Davy Jones' monstrous beast, the Kraken, an attack in which Jack is sacrificed by Elizabeth so the Kraken would not pursue the others if he tried to flee with them; thus Jack and the Black Pearl are sent to Davy Jones' Locker. Will, Elizabeth, Pintel, Ragetti, Marty, and Cotton (with his parrot) are the only survivors. When they return to Tia Dalma for help, she asks if they would be willing to do anything to save Jack and the Pearl. Gibbs is the first to accept the challenge.
Gibbs, along with Cotton, Marty, Pintel, and Ragetti, assist Captain Barbossa as they make their way to World's End to rescue Jack Sparrow. When Jack originally wanted to leave some people behind in Davy Jones's Locker, Gibbs was one of the only people Jack wanted to take back to the world of the living. He is one of the very few sailors to put up his hand when Jack asks if anyone came to save him just because they missed him, indicating a strong friendship between him and Jack. Jack also lets Gibbs throw his hat - as long as he gets it back.
In the closing scene of the film, Gibbs gets slapped by Jack Sparrow after Jack gets slapped by both Scarlett and Giselle. This is because Gibbs passed out drunk and let Barbossa steal the Black Pearl. Evidently, he sleeps with a Teddy Bear made of burlap. Despite falling asleep and causing the Pearl to be stolen he and Jack share a smile and their toast from the first film, and part as friends. He then stays behind in Tortuga with Scarlett and Giselle and tells them the story about Jack Sparrow which is what he told Will Turner in Curse of the Black Pearl while Jack tries to find the Fountain of Youth.
As part of a running gag within the film, during the Brethren Court scene, Pintel notices that the Nine-Pieces-of-Eight is in fact "just pieces of junk." Gibbs then explains that when the original court decided to imprison Calypso, they were all flat broke. When Pintel then suggests changing the name, Gibbs sarcastically retorts "What? To the nine-pieces-of-whatever-we-happen-to-have-in-our-pockets-at-the-time" and says it sounded real "piratey", referencing the lack of pirate creativity or actual wealth.
Ending up in London, Gibbs is arrested and is wrongly accused as Jack Sparrow. The real Jack Sparrow, posing a judge, comes to his friend's aid and gives him a life sentence instead of the expected death penalty so to get answers about the impostor posing as Jack to gather a crew. After being arrested by the royal guard, Gibbs managed to steal Jack's map and memorize it, possible from photographic memory or something, prior to burning it so that Barbossa would have no choice but to take him along to search for the Fountain of Youth. Eventually reunited with Jack, Gibbs uses his captain's compass during the climactic battle to find the Queen Anne's Revenge and get the bottled Black Pearl, stealing the rest of Blackbeard's trophies of war and treasure in the process.
Gibbs remains a part of Jack Sparrow's crew aboard the much smaller ship Dying Gull. However, with a long stretch of bad luck in piratical heists and Jack's behavior becoming much more unbearable as he keeps demanding a greater share of what little they can take, Gibbs and the crew finally abandon Jack. However, Henry Turner hires the crew to rescue Jack from a guillotine execution so that they can seek out Poseidon's Trident and defeat Captain Salazar.
Gibbs makes his debut into the Kingdom Hearts franchise in Kingdom Hearts III alongside Tia Dalma in their homeworld of the Caribbean, with events following what happened in At World's End. Gibbs is with Will, Elizabeth, Tia Dalma, Barbossa, and their crew, as they make their way into Davy Jones' Locker to find Jack and the Black Pearl, where they soon encounter Sora, Donald, and Goofy, who recognize Will, Elizabeth, and Barbossa, but have to be formally introduced to Gibbs and Tia Dalma. Once they reunite with Jack and the Pearl, they return to the Caribbean, where Sora learns that Davy Jones and Cutler Beckett are threatening to destroy piracy in the Caribbean. However, Sora soon has to make his way to Port Royal for repairs after his ship provided by Tia Dalma, the Leviathan, takes damage from the Heartless.
By the time he rejoins Gibbs and the others, Elizabeth has already been named Pirate King by the Brethren Court, and an attempt to appeal to help from Calypso revealed to be Tia Dalma in her bound human form, appeared to have been in vain. However, a stirring speech from Elizabeth to convince the crew of the Pearl to hoist the colors and show the Brethren Court that they are not afraid of Beckett's larger Royal Navy armada under the East India Trading Company flag convinces Gibbs and the others to fight back. Soon, Calypso makes her move to summon a maelstrom for the Black Pearl and the Flying Dutchman to do battle in with Sora attempting to support the Pearl with the Leviathan. However, after Jack, Elizabeth, Sora, Donald, and Goofy are forced to leave a mortally wounded Will on the Dutchman as it goes down after Jack helped Will stab Davy Jones' heart in the Dead Man's Chest, Gibbs warns Jack that Beckett is approaching on his flagship, HMS Endeavour, and suggests retreating while they still have the chance. Jack refuses, hoping Beckett will keep his end of their earlier agreement, but Beckett has the Endeavour prepare to attack the Pearl before the Dutchman resurfaces with Will its new captain. As Jack then gives the command to have the Pearl join the Dutchman in hitting the Endeavour in a double broadside, Beckett is left in a state of shock at having been outmaneuvered. On Jack's command, Gibbs relays the order to fire, and both ships unleash their fury on Beckett's ship. Beckett's Royal Marines abandon ship when they realize Beckett is unable to give orders and the Endeavour is doomed, and soon the powder magazines detonate, killing Beckett and finishing off the Endeavour. With the loss of their flagship and commander, the EITC/Royal Navy armada is forced to retreat in disgrace.
As the crew of the Pearl celebrate their victory, Sora notices Elizabeth gazing over at Will on the Dutchman, at which point, Gibbs explains to Sora that the Flying Dutchman must have a captain, and since Will is the new one, he's bound by the Dutchman to spend ten years ferrying the souls of the dead to the afterlife after spending one day on land, a steep price for their victory after having only become Elizabeth's husband a short while ago. Sora is left deeply upset by this, but Gibbs does his duty and provides a longboat for Elizabeth to travel ashore to spend her one day with Will before he starts his ten-year tenure at sea before he can set foot on land again. Afterward Gibbs stands with Barbossa, Donald, Goofy, and the crew as Jack assures Sora that the one day Will and Elizabeth have to say goodbye is enough time to bond, just like Jack and Sora do with their friends, family, and hearties.
While it is never explained why he left the Navy, when he asks James Norrington about his life, the latter responds that his life is like Gibbs' but "one chapter behind", implying that he may have been disgraced chasing pirates. It is also possible he was press-ganged into the Royal Navy, as piracy offered greater freedom at the time. Another possibility is that he was dismissed from the navy due to his drinking, as he is often seen swigging rum from a flask.