- "Seed"
It is revealed in this season that Andrea and Michonne (the hooded figure that saved Andrea's life in the Season 2 finale) have taken refuge at a game cooler, where Andrea is sick from influenza. Michonne raids a local pharmacy, bringing Andrea aspirin. Andrea unsuccessfully tries to convince Michonne to leave her, saying she can take care of herself. Andrea, however, is successful at convincing Michonne that they need to move out now instead of waiting a few days like Michonne had originally planned due to the walkers that surround their location. Andrea, Michonne, and her two pet Walkers flee out of a back entrance of the game building.
- "Walk With Me"
While traveling on the road, Andrea and Michonne see mysterious plumes of smoke rising in the distance. Going to investigate, they discover a crashed helicopter. Andrea stays hidden in the bushes while Michonne investigates, until the arrival of The Governor and his group. Michonne kills her pet walkers, attempting to prevent the men from detecting their presence. However, an unidentified person sneaks up on them, and a man's voice instructs them to lower their weapons and turn around. As Andrea and Michonne comply with the request, the man holding them at gunpoint is revealed to be Merle Dixon. Surprised to see Merle, Andrea passes out.
Andrea drifts in and out of consciousness while riding in a vehicle, but notices a dead corpse hanging from a tree and several abandoned vehicles before entering Woodbury. She is then taken care of by Dr. Stevens while Michonne watches. Merle comes into the room and asks about Daryl. Andrea tells him briefly what has transpired since she last saw him. The Governor arrives, but refuses to allow them to leave after dark or return the women their weapons. He also reveals that they are all infected, and that everyone will come back as walkers no matter how they die.
The Governor shows Andrea and Michonne outside and welcomes them to Woodbury, showing off his impressive fence they have built around the town, and how they protect it. The following day Andrea and Michonne learn more about Woodbury from Rowan. Andrea seems to be impressed by The Governor and his accomplishment of creating a safe town, though Michonne seems more hesitant to trust him. Andrea grows tired of Michonne's aloof nature, telling her that she knows little to nothing about her. Andrea is friendly with The Governor when he returns from his mission to find Lieutenant Welles' comrades.
- "Killer Within"
Andrea is preparing to leave Woodbury with Michonne, who says they should head for the coast and perhaps find a boat. Andrea is skeptical of this plan, but knows Michonne is suspicious of The Governor.
Andrea gives a map to Merle, so that he can find Hershel's farm and search for Daryl. She talks to The Governor one last time, and he tells her his name is Philip. She returns to Michonne, reluctant to leave, and convinces her to stay in Woodbury a little longer.
- "Say the Word"
Woodbury is busy preparing for a day of celebrating as part of a party put on by Philip. Andrea enjoys the day's festivities, including cold drinks and an inspiring toast by Philip. When she questions Milton Mamet about the big event for the night, he avoids telling her.
She is told later by Merle that Philip wants to talk to her, and that it is urgent. Philip informs her that Michonne has broken into a private area and slayed a group of captive Walkers, and that she threatened Philip with her sword. When Andrea asks why he was keeping Walkers captive, Philip does not give her the answer just yet.
Going back to the room she shares with Michonne, Andrea asks an agitated Michonne why she did those things. "You're freaking me out," Andrea says, watching her hurriedly pack their things. Michonne continues to go on about how suspicious Woodbury really is, and Andrea says, "You are not making any sense." However, she decides to leave with her anyway.
As the pair of them are walking towards the gate to leave, Merle spots them and prevents them from going. He speaks briefly to a guard, and when Andrea tries to talk to him, he says, "I'm going to need you to back up." Confused, she turns to Michonne and asks if they can stay a little while longer. Andrea says that Woodbury is the refuge they have been seeking for 8 months, and that they should stay. Michonne gives her an ultimatum: either come with her, or stay in Woodbury without her. When Andrea hesitates, Michonne scoffs, "You just slowed me down anyway", and leaves her.
Later, while she is sitting at a bench and feeling hurt, Philip approaches Andrea. He comforts her, saying he has something in mind that will help blow off steam. That night, Andrea and the rest of Woodbury look on as Merle and Martinez face off in an arena of Walkers. The two men kick and punch each other, surrounded by Walkers, while Philip and the rest of Woodbury cheer.
Andrea becomes angry, accusing Philip of being "sick". Philip pulls her aside and says that they have pulled out the zombies' teeth, so that the men cannot be harmed and that it is just for fun. Philip says that he is teaching the people to be brave. Andrea still appears upset by this, as Merle defeats his opponent.
Carl, still believing that Andrea is dead, mentions her when listing the names of deceased female members of the group as possible names for the newborn baby.
- "Hounded"
Andrea has been accepted as a member of Woodbury now, and wants to contribute in any way she can. She asks Philip if she can guard the wall, and he agrees.
Andrea meets Haley while guarding the wall, who reveals that she had lost her father and brother. When a walker approaches, she fails to kill it with her bow. Andrea jumps from the wall, knocking down the walker and stabbing it in the head.
Later, she is scolded by Philip, who does not want anyone leaving the wall. Andrea admits that she actually liked the arena fighting, but it bothered her to like them. Philip assures her nothing is wrong with liking a fight.
Sparks fly between the two later, and she ends up kissing him. They get more passionate later on, and she ends up having sex with him.
- "When the Dead Come Knocking"
Andrea is invited by The Governor to witness Milton's conduction of an experiment on the ailing Michael Coleman. Andrea questions if Milton has ever seen reanimation, to which he denies and explains that he was an only child and his parents had passed away while he was young. She later witnesses Michael reanimating and Milton repeats the experiment. The walker grips onto the bed and Milton believes that it was a positive response. Andrea believes it was just a random reanimation reaction. Milton unties Michael's restraints and repeats the experiment once more. The reanimated Michael does not hesitate and pounces on him, but before he can bite him, Andrea stabs it in the head while Milton, shaken, states that he will study his work and walks off.
- "Made to Suffer"
Andrea informs The Governor that she wants to assist Milton in cremating Mr. Coleman; he remarks that "Woodbury's starting to grow on you." She is later seen with The Governor as he assembles a group to kill Rick and the other intruders. She volunteers to help the others, but The Governor insists that she stay behind; she nonetheless takes a gun and helps the guards shoot at Rick and the others, though she can't identify them due to the smoke. She spots Oscar and fires at him, but misses her shots.
Andrea later discovers The Governor, who had been mutilated by Michonne, and draws her gun at the latter, but doesn't fire. After approaching The Governor to comfort him, Andrea notices the tanks containing the severed heads of walkers and the corpse of Penny. She demands to know why he had them there. The Governor gives her a vague answer about the heads before brushing her next question about Penny off. Andrea is later seen at the gathering of Woodbury citizens when The Governor denounces Merle a traitor and is shocked when he reveals their prisoner to be Daryl.
- "The Suicide King"
Andrea tries to talk Philip out of the deathmatch between Daryl and Merle, but to no avail. When the Woodbury survivors are distraught after the attack, Andrea manages to deliver a motivational speech, telling them that they have to persevere and assist in calming them down. Andrea also learns that her old group were the ones responsible for attacking Woodbury and causing the death of seven residents.
- "Home"
The Governor visits Andrea, requesting her to take over leadership of Woodbury, insisting that he had "screwed up." Andrea later goes searching for Martinez and The Governor, who both went missing. Milton dodges her question, suggesting that The Governor may have went on a supply run. Andrea, however, doesn't believe his claims and walks off.
- "I Ain't a Judas"
Andrea talks with The Governor, who tells her that the prison group attacked them first while he was simply attempting to negotiate. He tells her that they are "bloodthirsty." He also tells her that if she goes to the prison, she is to stay there. Andrea talks with Milton, and wants him to cover for her as she sneaks out to go the prison to make peace between Woodbury and the prison group. Milton and Andrea capture a walker in the woods to use as a deterrent. Andrea hacks both of the walker's arms off and then uses a rock to curb-stomp the walker's teeth out to prevent it from biting. Andrea and Milton are saved by Tyreese Williams's group when another walker appears. Andrea arrives at the prison, learning of the fates of Shane, Lori, and T-Dog. Andrea tries to make peace, but Rick and the others make it clear that they want to retaliate against Woodbury and The Governor. Andrea learns that The Governor lied about who shot first from Rick, and Andrea's negotiation ends when Rick storms off after Andrea refuses to get them inside of Woodbury. Andrea accuses Michonne of poisoning the group, but Michonne argues that she was telling them the truth. While talking with Carol, Carol tells her to sleep with The Governor and give him the best night of his life, and then to kill him while his guard is down. Before departing, the group gives her a car and Rick hands her a handgun and a knife. She arrives back to Woodbury and sleeps with The Governor. While he is asleep, she stands over his bedside with a knife, contemplating Carol's plan. Andrea, however, puts the knife away and peers out of the window, unable to go through with the killing.
- "Arrow on the Doorpost"
Andrea, along with Milton and Martinez arrive at an abandoned farm's barn as set by her, in order to get Rick and Philip to talk about the situation between the two groups. Andrea then, noticing the meeting began without her, strides inside the barn and tries to mediate the situation but is told by Rick that he knows about the raids, the heads and about Maggie.
Later, she tells the both of them to calm down after Philip demands Rick's surrender, and is then kicked out by The Governor. While waiting outside the barn, a small group of walkers approaches Andrea, Daryl, Hershel, Milton and Martinez, which causes Andrea, Daryl and Martinez to go kill them.
Andrea asks Hershel what Philip did to Maggie, which he answers saying "He's a sick man." Andrea is in despair and says she can't go back to Woodbury. Hershel agrees that she belongs at the prison, but warns her that once she leaves, she can't go back.
When Rick and Philip are done talking, all of them enter in their cars, causing Andrea to join Woodbury again. When they get back to Woodbury, Philip thanks her for setting up the meeting, but doesn't tell her about his plan of killing Michonne and the rest of the group. Andrea says she is glad she could help.
- "Prey"
Milton tells Andrea about how he saw the torture room that Philip made for Michonne. He takes her to see it, and they look at all the tools that Philip plans to use. Milton tells her to go to the prison and tell them that they have to leave. She instead says that she must kill Philip. He walks in, and Andrea, in an overlooking room, points her gun through the shutters on the window. Milton forces her to put it down. Later, Martinez tells her to give him her gun, for "precautions". Andrea is later seen climbing over a wall that Tyreese and Sasha are guarding. Tyreese tries to stop her, only to have Andrea pull a knife on him. After a little negotiation, they allow her to leave. She starts a steady run, knowing that Philip will soon find out. She is running down an unknown road when she hears a car. She runs into the near woods and hides behind a tree. She is grabbed from behind by a walker, and two more approach her. She blocks them with her leg, and then kills them. She is next seen in an empty field when she hears the car again. She ducks down, but it's too late. Philip starts following her as she runs away. She goes through some debris, and Philip has to go around. She winds up at an abandoned warehouse. While inside, she accidentally tips over a bucket of tools, alerting Philip. She ends up finding a door. She opens it, finding many walkers on the stairwell inside. She closes the door, and turns around, seeing that she is cornered by Philip. She opens the door again and hides behind it, allowing the walkers to attack him. She finds a way out and leaves. She later arrives at the prison, trying to signal Rick, who is on guard in a watchtower. She is then grabbed and pulled down by Philip. Rick sees this out of the corner of his eye, and aims his rifle down there, only to come up empty. Philip somehow makes his way back. She is then seen, chained to a chair in the torture room.
- "Welcome to the Tombs"
Andrea is seen still restrained to The Governor's torture chair. After Milton is beaten by The Governor, he is ordered to kill Andrea. When he refuses and attempts to kill The Governor instead, he is stopped and stabbed by The Governor and left to die but not before Milton leaves some pliers behind the chair. He tells Andrea about the pliers and orders her to stab him in the head once she frees herself. She tries to kick the pliers so she can grab them but she cannot in her boots. She takes off her boots to get the pliers more quickly as Milton slowly dies. After some struggle, she gets them and begins to free herself. As she begins to cut through her restraints, Milton reanimates. She manages to get one arm free as the now undead Milton stands up, ready to attack. She tries desperately to get the other arm free but is too late, for as she stands up, Milton bites her. She quickly dispatches Milton before falling to the floor. Later, Rick, Michonne, Daryl, Tyreese, and Sasha arrive at the torture room and find a pool of blood outside the door. They go in, find Milton's body, and find a bitten Andrea sitting against the wall. Michonne cries as she sees that Andrea has been bitten. Andrea requests that she commit suicide to avoid reanimation. Rick gives her his revolver and goes outside with Daryl. Michonne stays with her friend as she commits suicide, preventing reanimation and ending her life. Her body is later brought back to the prison for burial.
