On another occasion, Sawyer carries out a "long con" (large-scale con) on a divorced woman named Cassidy who is known for being less gullible than his usual victims. He sets up the usual con and spills his cash over the ground, only this time with fake bank notes. Cassidy realizes he's trying to con her from the moment he spills the money, and tells him that his con wouldn't have worked anyhow because she received no money after the divorce. Instead of being mad, however, she asks him to teach her his profession. After learning a few basic tricks, Cassidy soon asks Sawyer to pull off a long con. He tells her that such a con requires money, and she reveals that she actually received $600,000 from her ex-husband. He pretends to begin a long con with her, using her money to set it up, but in fact he simply plans to take the money. However, she has begun to grow on him, and he wavers on his con. While visiting the diner of Kate's mother, his partner (played by Kevin Dunn) forces Sawyer to resume his con on threat of death. He goes back to Cassidy and tells her that he has been conning her, and warns her of a car parked outside. He stuffs the money into a bag and tells her to run away with it, and he will take the blame for the missing money. When she runs off, he takes the real money (having given her fake bank notes) and returns to the car, which was actually empty.
Cassidy presses charges against Sawyer for conning her, and he is sent to prison. Cassidy visits him and informs him that she has since given birth to a girl named Clementine. While in prison, Sawyer befriends a man named Munson, who was sentenced for a white-collar crime. He cons him into revealing where Munson hid the money that he stole; as a result, Sawyer's sentence is cut short, and the money he receives is deposited in an anonymous bank account for Clementine by his request. Later, as Sawyer is seducing another woman, another partner (played by Robert Patrick) informs him of the whereabouts of the original Sawyer who conned his parents. Sawyer travels to Australia to confront the man, and shoots him. Before he dies, Sawyer realizes that his partner had conned him into killing someone who owed money to an important person. Sawyer also encounters and drinks with Christian Shephard at a bar. While still in Australia, Sawyer is arrested, at the same station visited by Boone, for assaulting Warren Truss during a bar fight. As a result, Sawyer is deported from Australia and banned from returning; he leaves on board Oceanic Flight 815, his seat number being 15D.
Upon landing on the island, Sawyer almost instantly clashes with the other survivors. He initially accuses Sayid of being the terrorist that caused the crash. Despite this, he joins him, along with Kate, Charlie, Boone and Shannon on a hike to send out a distress signal. Upon returning, Sawyer searches the plane wreck for anything and everything he can find and keeps them for himself, causing the other survivors to bargain with him for items. He and Jack clash over the attention of Kate on regular intervals. After Jack is caught in a cave-in, Sawyer locates Kate in the jungle and eventually informs her. When Shannon experiences asthma attacks, Sawyer is immediately under suspicion of possessing her inhalers after Boone sees him with one of his belongings. After being interrogated by Sayid, he tells Kate that he doesn't have them, causing an enraged Sayid to stab him in the arm. He is then confronted by Kate regarding his selfish actions, and tells him to change his ways by cooperating more with the survivors, to which he reluctantly agrees.
In the jungle, Sawyer and Kate discover a case, carried on the plane by the Marshall, and the two constantly fight over its ownership, until Jack hides it in the jungle. Soon after, Sawyer becomes constantly harassed by a boar, and seeks Kate's help in finding it. Upon cornering it, however, Sawyer decides to let it go. After learning about Michael's plan to build a raft, Sawyer asks for a place on board, to which he is granted. However, after someone (later revealed to be Walt) sets the raft on fire, Sawyer and Michael blame Jin and Sawyer takes him to the beach with the intent of beating him. Once the matter is solved, Sawyer experiences headaches and, after consulting Jack, is prescribed reading glasses, made from pairs found in the wreckage. His voice also calms the new-born of survivor Claire.
The day before the raft sets sail, Sawyer and Kate clash once more, this time over his place on the raft. While Kate placed a good argument, Sawyer revealed her past life as a criminal to the survivors, securing his space on the raft. The next day, Sawyer, Michael, Walt and Jin set sail on the raft. When a piece of the raft breaks off, Sawyer is the first in the water to retrieve and re-attach it. He also begins reading through the survivors' personal messages, which are kept in a bottle. That night, they encounter a small boat and begin celebrating their rescue. However, they soon reveal themselves as the Others, and demand they hand over Walt. In an attempt to prevent Walt's abduction, Sawyer is shot in the shoulder before the raft is destroyed by the Others, who leave with Walt.
On one such occasion, Sawyer releases Jack and Locke from the armory after Michael locks them in to search for Walt alone. Sawyer agrees to join them as they follow, only to encounter the Others. After revealing to have Kate held hostage, Sawyer, Jack and Locke reluctantly hand over their guns for her safety. Unlike Jack, Sawyer sympathizes with Kate's actions. Soon after, Sawyer sets up a long con, with the help of Charlie, in order to gain possession of the camp's entire firearms and medicine, using Sun as a victim of a faked abduction attempt. Upon succeeding this feat, Sawyer is challenged by Jack to a game of poker with the medicine as the prize, to which Sawyer loses. Sawyer later gives Sun a pregnancy test upon request, and proceeds to inform Bernard and Jin about her suspected pregnancy.
Sawyer also uses his possession of the medicine to his advantage, and mocks Hurley when he admits to seeing things, only for his tirade to backfire. He also refuses to help Bernard create an S.O.S. sign on the beach. He is soon confronted by Ana Lucia, demanding that he give her a gun. She seduces him, and steals his own gun from him. Upon discovering this, Sawyer, along with Jack, Locke and Kate, heads for the hatch, where they discover Michael injured, Libby fatally wounded and Ana Lucia already dead. Michael asks Sawyer if he will go with him to the Others' camp, to which he agrees. After the funeral of Ana Lucia and Libby, Sawyer joins Michael, Jack, Kate and Hurley on the trek, where they are suddenly ambushed by the Others, tied up and taken to a pier. While Michael (along with Walt) leave the island, and Hurley is released, Sawyer is taken away by the Others, along with Jack and Kate.
Sawyer schemes with Kate and eventually decides to put into practice an elaborate escape plan. However, he is caught by Ben who knocks him unconscious with a baton. When he wakes up he is on an operation table with a large amount of stitching over a scar on his chest. Ben visits him and shows him a demonstration where he apparently kills a white rabbit with a painted number on its back by shaking the cage and scaring the rabit. He tells Sawyer that, like the rabbit, he has placed a pacemaker in Sawyer's heart that will explode if his heart rate exceeds a certain point. Sawyer will know that he is in danger when a stop watch that Ben gives him starts to beep. Ben tells him that this should stop his escape attempts, and that if he tells any of this to Kate he will implant one in her heart too. When he returns to his cage he is violently beaten by Pickett, and unable to defend himself. Picket says he'll only stop once Kate says that she loves Sawyer, which she does to get Pickett to stop beating him.
Kate, who has realized that she is small enough to fit through the bars at the top of her cage, gets frustrated with Sawyer when he refuses to escape with her telling her that it is every man for himself, and that she should leave without him, which she doesn't. Later on Sawyer is visited by Ben who takes Sawyer on a hike with him across the island. They eventually stop atop a large hill where Ben admits to Sawyer that he had conned him, and that there is in fact no pacemaker in his heart. He then shows Sawyer that they are on a small island just off the main one, and that there is no way of escaping anyway, so he should stop trying.
When he returns to the cages, dejected, he has sex with Kate and is then held at gunpoint by Pickett, who is using Ben's tumor operation as a distraction to finally kill Sawyer. Just before he can, however, he is radioed by Tom who tells him that Jack is threatening to kill Ben unless Kate and Sawyer are released. Sawyer uses this distraction to beat Pickett up and, along with Kate, make his escape. In the jungle they are helped hide from the now angrily pursuing Pickett by Alex Rousseau. Sawyer and Kate help Alex rescue her boyfriend, Karl, from a hatch on the island where he is being brainwashed, and in return are given a canoe to escape onto the main island in, with Karl. On the beach Pickett finally catches up with them, but is shot dead from behind by Juliet who had orders from Ben to help their escape.
When they arrive back on the main island Sawyer clashes with Kate over his subsequent decisions to leave Jack behind, and then to let Karl free. When they arrive back at the survivors' camp, Sawyer keeps his distance from Kate and has a beer fueled joy riding session with Hurley, Jin, and Charlie in an abandoned Dharma truck that Hurley found in the jungle. When he returns to the beach he discovers that Kate has gone off with Sayid and Locke in order to find Jack. In this time he develops a friendship with Hurley, often playing him at table tennis. Hurley surprises Sawyer by telling him that in the absence of Jack, Locke, Kate, and Sayid the rest of the survivors are going to start looking up to Sawyer as their leader. Sawyer takes this challenge well, and bonds well in this time with the other survivors. When Kate and Jack finally return Sawyer is outraged to find that they have brought Juliet with them. He briefly teams up with Sayid in an attempt to get information on the Others out of her, however they ultimately fail.
Sawyer starts up a relationship with Kate, however he begins to get the feeling that she is using him to make Jack jealous. One night Sawyer is visited by Locke who tells him that he has captured Ben, and that he wishes to show Sawyer this. He takes Sawyer to the Black Rock and tricks him, locking him in a room with a man, not Ben, who has been bound and gagged by Locke. The man reveals that he is Anthony Cooper, Locke's father, and that he is a conman who also goes under the name of Tom Sawyer. Sawyer realizes that this is the man whom he has been searching for and, after Cooper mocks his letter of vengeance, Sawyer strangles him to death in a fit of anger. Now Sawyer was no more. He reverts back to James. Before he heads back to the beach Locke presents him with an audio tape proving that Juliet is still working for the Others, and that the Others are preparing a raid on the survivors. When James shows this tape to Jack however Jack shocks everyone by saying that he knows about the raid, and that Juliet has been secretly working with him on a way plan to double cross the others.
James joins the survivors as they hike across the jungle to the radio tower, however when Sayid, Jin, and Bernard are captured by the Others he decides to go back with Juliet to rescue them. Despite having no guns, their rescue is a success as they are vitally helped by Hurley and the Dharma truck. Two of the Others are killed and the third, Tom, is captured before James proceeds to shoot him in vengeance for 'taking the kid off the raft.'
Sawyer, Claire and Miles soon come across the bodies of Danielle and Karl. After leaving the area, they decide to settle down to make camp, however during the night Claire takes off into the jungle. Sawyer wakes up the following morning and Miles tells him that Claire walked into the jungle in the middle of the night with someone she called "Dad". A short while later he hears Aaron crying and runs off to find him alone in the jungle. Afterward, he and Miles, along with Aaron move on, where they meet Jack and Kate in a small field. Jack and Kate were in the process of moving towards the helicopter from the freighter, with Jack inadvertantly thinking the dropped satellite phone from Frank was a message to follow the crew. Sawyer then informs Jack and Kate that Claire walked off and that the freighter's crew are up to no good. He hands Aaron over to Kate and tells her to go back to the beach with Miles and the infant, while he insists on going with Jack to face Charles Widmore's men. The two then find the helicopter, discover Frank handcuffed to the seats, and are told the men are heading towards Ben. Sawyer thn tells Jack that Hurley is with Ben and the two head off to rescue Hurley.
Jack and Sawyer eventually find Hurley and Locke at the Dharma Orchid station. After Jack finishes talking with Locke, Sawyer and Hurley meet up with Kate, Sayid, and Lapidus at the helicopter. As they are heading for the freighter, Lapidus notices that the helicopter is quickly losing fuel. Sayid deduces that the this is the result of a bullet hole in the gas tank. Sawyer, along with the other passengers, discard all unnecessary items to lessen the weight load. Lapidus comments that he wishes they were still a couple hundred pounds lighter. Sawyer then whispers something to Kate, presumably about his daughter, then proceeds to kiss her and jump out of the helicopter. Sawyer manages to swim safely back to the Island and encounters Juliet, who directs his attention to smoke coming from the ruins of the freighter. As the two lie on the beach drinking rum, they disappear along with the Island to its new location.
After the Oceanic Six (Jack, Kate, Hurley, Sun, Sayid and Aaron) leave the Island, flashforwards in Something Nice Back Home reveal that Kate is doing undisclosed favors for Sawyer, who, according to Jack, 'chose to stay on the island'.